Fourth Doctor

The Fourth Doctor was the fourth incarnation of the Time Lord known as the Doctor. He left all ties of his previous incarnation's exile behind on Earth, setting off to travel the cosmos. He initially travelled with Sarah Jane Smith and Harry Sullivan, but Harry chose to remain on Earth when the opportunity arose. The Doctor and Sarah continued on their adventures until the Doctor was summoned to Gallifrey, necessitating that he leave Sarah Jane behind as humans were not allowed on Gallifrey at that time.

After leaving Gallifrey, he met and travelled with Leela of the Sevateem. During his travels with Leela, the Doctor gained a new companion in the robot dog, K9. Returning once more to Gallifrey to stop an invasion, Leela and the original K9 stayed behind there. On the White Guardian's orders, the Doctor began looking for the Key to Time with fellow Time Lord Romana and K9 Mark II. Once that search was concluded, the Doctor and a newly-regenerated Romana went on the run from the Black Guardian. They accidentally passed into the smaller universe of E-Space.

During his travels in E-Space, the Doctor gained a new companion in the young mathematical genius Adric. Romana and K9 stayed behind in E-Space as the Doctor and Adric departed for N-Space.

Once again encountering his old enemy the Master, the Doctor and Adric met a Traken girl named Nyssa. She later joined them, along with the human Tegan, to help him prevent the destruction of the Universe by entropy. While stopping the Master from using this threat to blackmail the Universe into servitude, the Doctor fell from the Pharos Project telescope and regenerated for the fourth time.

Premature Debut
The Third Doctor first regenerated after he fell off a roof during a struggle. However, the Nurazh attempted to take over the Doctor's mind, but, unable to cope with two Time Lord minds at the same time, perished, thus healing the Doctor back to his third incarnation. Jo Grant saw the Fourth Doctor long enough to describe him to the Third Doctor. (ST: The Touch of the Nurazh)

Post-regeneration
The Doctor's third incarnation regenerated some time after the radiation from the Great One's lair took effect upon him. He returned to Earth to end his time in the company of Sarah Jane and the Brigadier after being lost in the Time Vortex for an unknown amount of time. K'anpo Rimpoche arrived and gave the Doctor a push for his regeneration, which he warned would scramble his mind. (DW: Planet of the Spiders)

Once he had regenerated, the Doctor suffered delirium, mumbling random things from his adventures, and was physically exhausted. He was put in sickbay, where Harry Sullivan kept watch on him. However, the Doctor managed to outwit him and get to the TARDIS to choose his new wardrobe. Though he still had a hard time realizing things around him, the Doctor was asked by the Brigadier to help deal with Think Tank and their K1 robot, which had gone insane from so many contradictory orders its programming should have prevented it from doing. Afterwards, he took Sarah Jane Smith and Harry Sullivan to travel with him in the TARDIS, unofficially abandoning his laboratory. (DW: Robot)

Adventures with Sarah Jane
The Doctor's first trip with his companions was intended to be a quick trip to the Moon. However, due to Harry messing around with the console controls, the TARDIS landed on Space Station Nerva, where humanity had been cryogenically suspended to await Earth's recovery from solar flares. There, the Wirrn wished to use the humans as food and incubators for their kind. Luckily, Noah, a human converted in a Wirrn, retained his humanity and tricked the Wirrn into a suicide. Afterwards, on behalf of the space station, the Doctor went down to Earth with Harry and Sarah Jane to fix the transmat relay. (DW: The Ark in Space)

Once on Earth, they found the Sontaran Styre there conducting experiments on humans as a prelude to an invasion. The Doctor defeated his plans, allowing the resettlement of Earth to proceed. The Doctor and his companions transmatted back to the space station. (DW: The Sontaran Experiment)

Intercepting their transmat beam, a Time Lord appeared to the Doctor and forced him to undertake a mission on their behalf: intervene in the creation of the Daleks. He was either to prevent it or to induce the Daleks to develop into less dangerous creatures. Although he was morally unable to commit genocide by destroying the entire race, he did manage to delay their advancement. It was during this time the Doctor had his first encounter with the insane creator of the Daleks, Davros, and tried unsuccessfully to convince him to make the Daleks into a force for good instead of the murderous monsters that they would become. (DW: Genesis of the Daleks)

Departing Skaro via the Time Ring that was given to him, the Doctor, Harry, and Sarah Jane ended up back on Space Station Nerva. However, it was later in its time line, when it orbited Jupiter and the original colonists had long ago repopulated Earth. While waiting for the TARDIS to catch up with them, the Doctor became involved with stopping a Cyberman attack on Voga, the planet of gold. The Doctor ultimately stopped them from blowing up the planet and saved Sarah Jane from the fatal bite of a new variant of Cybermat. (DW: Revenge of the Cybermen)

Upon being contacted by the Brigadier via a space-time telegraph to return to Earth for assistance, a great deal of time since his departure from UNIT headquarters (Robot) (something that angered the Doctor as he hated to work), the Doctor encountered the Zygons and helped defeat them. Though the Doctor offered him a quick lift back home, Harry decided to end his travels with the Doctor, possibly because of all the danger they went through. (DW: Terror of the Zygons)

The Doctor had begun, even more so with this regeneration, to break his ties with Earth. However, despite intending to resign from UNIT, (DW: Pyramids of Mars) the Doctor never formally left his position as their unpaid scientific adviser; other scientists had to be hired to take his place during his absence. (DW: The Sontaran Stratagem, Planet of the Dead) Soon after Harry's departure, the Doctor and Sarah encountered anti-matter monsters. (DW: Planet of Evil) Attempting to return to UNIT, the Doctor had to prevent the last of the Osirians, Sutekh, from escaping his prison pyramid on Mars and bringing destruction to the Universe. Though unsuccessful in stopping Sutekh's release, the Doctor was able to defeat him by ageing him for 4000 years, ageing him to death. (DW: Pyramids of Mars)

Taking a trip back to present day Earth, the Doctor seemingly found himself in a town Sarah Jane had previously visited, only to find it was a facsimile populated by androids under the control of the Kraals. The Kraals' own world had become uninhabitable, leading them to plan on wiping out Earth's population with a virus, then populating the planet themselves. The Doctor stopped them with the help of UNIT. (DW: The Android Invasion)

The Doctor next found his TARDIS forced to land on Karn by the Time Lords. There, he was tasked with preventing the Frankenstein-esque resurrection of the evil Time Lord Morbius, but nearly died as a result. The Sisterhood of Karn used the Elixir of Life to heal him at the cost of one of their own to the fire that made the elixir. (DW: The Brain of Morbius)

Soon after, the Doctor helped stop a Krynoid victim from taking over the Earth with plants, with the help of UNIT once again. This was his last direct encounter with UNIT for many years. (DW: The Seeds of Doom)

During a trip in space, the Doctor accidentally brought Helix Intelligence to San Martino in the 15th century, where it planned to dominate the human race by using the Brotherhood of Demnos as its agents. The Doctor was able to stop this by reversing the energy flow, which drained the servants of the energy they were given, killing them in the process, but saving Earth. (DW: The Masque of Mandragora)

Later, the Doctor and Sarah Jane ended up in a quarry, where an explosion nearly cost Sarah her life. The Doctor found that she had obtained a petrified hand in the rubble and was possessed by Eldrad, who forced Sarah to take it to a nuclear power station, where it regenerated into a female rock-based humanoid modelled on Sarah. The Doctor complied with Eldrad's request to be taken back to Kastria, where Eldrad's true male form was restored. But it was revealed that Eldrad had gone insane and caused the end of his species; with his people extinct, he planned to rule Earth, but the Doctor managed to trip him into a pit.

While preparing to leave for new adventures, the Doctor received a telepathic summons from Gallifrey and was forced to leave Sarah behind as humans were not allowed. (DW: The Hand of Fear) When returning Sarah to Earth, he "blew it," accidentally not leaving her in her home town of South Croydon. He later defended his leaving her behind with the second reason of her becoming too detached from her life on Earth. (DW: School Reunion)

Return to Gallifrey
Upon return to Gallifrey, the Doctor tried to prevent the death of the Lord President, but was unsuccessful, ending up getting the blame instead for his murder. The Doctor put off execution by announcing his own candidacy for Lord President, buying him enough time to find a degenerated Master was responsible. Defeating the Master, the Doctor left his former teacher Borusa in charge. Throughout the adventure, he also re-experienced, to his disgust, the decadence of Time Lord civilisation. (DW: The Deadly Assassin)
 * The Doctor travelled for an unknown period of time alone following his departure from Gallifrey.

Time alone
The Doctor had many adventures on his own.

The Doctor visited a planet colonised by the Mordee expedition, and encountered the colony ship's powerful computer, Xoanon. He inadvertently accidentally imprinted his own mind on the computer, leaving it with multiple personalities. (DW: The Face of Evil)

New friends
The Doctor returned to the planet colonised by the Mordee centuries before, where he found that he was remembered as an evil god by the descendants of the colonists. Descendants of the colonist's survey team had become a warrior tribe called the Sevateem, while descendants of the technicians had become a technologically advanced tribe called the Tesh. After the Doctor cured the computer, one of the Sevateem, Leela, joined him on his travels. (DW: The Face of Evil)

The Doctor brought the intelligent but uneducated Leela to many locations in human history, teaching her about science and her own species' past. In Victorian London, the pair encountered the magician Li H'sen Chang and his master, the self-styled Weng-Chiang, who was actually the 51st century criminal Magnus Greel. (DW: The Talons of Weng-Chiang)

The Doctor, having become the host of the Nucleus, travelled to the Bi-Al Foundation medical centre in the year 5000, where its Swarm spread further. The Nucleus brought itself out of the Doctor's body and into the macro world to hatch more young. The Doctor travelled to Titan Base, where a hive of Swarm lay. The Doctor mixed the oxygen canisters with the methane atmosphere of Titan, blowing up the base. While there, he brought along Professor Marius' dog K9 to fight the Swarm-infected humans.

Unable to return to Earth with K9, Marius gave the Doctor K9 as a gift. (DW: The Invisible Enemy)

The Doctor later traced the source of a Time Hole to where a group of scientists had been experimenting on a skull called Eustace. Much to his horror, the Doctor found that "Eustace" was actually the skull of a Fendahl Golden Core, but managed to stop a cult from nearly causing the end of the world. He later tossed the skull into a star to be rid of it and its evil once and for all. (DW: Image of the Fendahl)

The Doctor later helped the people of a Pluto colony rebel against the Company, that was oppressing them with high taxes, even saving a person from committing suicide. (DW: The Sun Makers)

The Doctor helped what remained of the original Minyans locate their race bank and home planet. He also defeated the Oracle, a machine that had been selfishly ruling the planet in place of its populace. (DW: Underworld)

Lord President of Gallifrey
Returning once more to Gallifrey and, posing as vainglorious and power-mad, the Doctor sought and attained the office of Lord President as part of a scheme to save his home world from an invasion force of two separate enemies, the Vardans and the Sontarans. Leela decided to remain on Gallifrey with K9 and Andred, a Gallifreyan in the Chancellory Guard she had fallen in love with. However, the Doctor left the Capitol with K9 Mark II, in a crate, planning to continue adventures with his beloved dog. (DW: The Invasion of Time)

Battle with the Hornets
While travelling on his own, the Doctor took up sojourn in a cottage in Sussex called Nest Cottage in the 21st century. He investigated a string of murders, where he found the murders were caused by stuffed animals, which came from a taxidermy factory, ran by a passionate taxidermist called Percy Noggins, who was angered by the disposal of stuffed animals from museums and stately homes. Upon meeting the Doctor, Percy sent a small army of stuffed animals to kill the Doctor, since he had deemed him a threat. Where the Doctor discovered the stuffed animals were animated by alien Hornets, who wanted to take control of the Doctor's mind. When he returned to the factory, the Doctor had found out that Percy Noggins had come into contact with the Hornets, and took control over his mind, using his desire for revenge on mankind so he would work with them in their plan to use taxidermy animals to conquer the world. This was the Doctor's first encounter with the Hornets (from his perspective), but the Hornets had somehow encountered the Doctor before, on numerous occasions, over many centuries. The Doctor lured all the Hornets towards Nest Cottage, where the TARDIS' dimensional stabilisers put up a force shield to prevent them getting out and taking over the world. (AG: The Stuff of Nightmares)

The Doctor later travelled to 1932 Cromer to investigate previous incursions of the Hornets on Earth, where he found a dancer called Ernestina Stott stealing some ballet shoes with the remains of feet inside them, owned by Mrs Wibbsey, curatress of the Cromer museum, both under the influence of the Hornets. Upon discovering the significants of the ballet shoes in his investigations, the Doctor had found out that they where the ballet shoes of a dancer called Francesca, just like Ernestina, and they were being used by the Hornets as a hive for their dormant swarm, which Mrs Wibbsey had been taking care of for years. The Hornets attempted to use Mrs Wibbsey to shrink the Doctor and Ernestina down, putting them inside a doll's house filled with deadly dolls, animated by the Hornets, but the Doctor escaped and found a way to bring them back to normal. After that the Hornets tried to occupy Ernestina's body, making her their new hive, but the Doctor stopped them by removing the ballet shoes before they could take full possession of her. He confiscated the doll's house and the ballet shoes and placed Mrs Wibbsey under his protection in Nest Cottage as his housekeeper and regularly mesmerised her to prevent the Hornets from taking over her mind. (AG: The Dead Shoes) However, the Doctor later discovered that Ernestina was still carrying the dormant Hornets inside her, who then made contact with her grandson, Percy Noggins, the taxidermist who cooperated with the Hornets in their scheme to control stuffed animals. (AG: A Sting in the Tale)

The Doctor then travelled to 1832 Blandford to investigate the Circus of Deights, whose arrival coincided with disappearances in the village. During this trip to Blandford, the Doctor encountered a girl called Sally, whose father had prevented her from attending, due to his belief that the circus was evil, and corrupted the people of the village. As well as meeting Dr Adam Farrow, whose sister Francesca had run away with the Circus of Delights, to become "The Bearded Lady of the High Wire." Sally and Farrow accompanied the Doctor in his investigation of the circus, where the Doctor discovered that the Hornets were responsible for odd goings-on at the circus, lead by the dwarf ringmaster, Antonio. It was discovered that the Hornets had been taking possession of members of the village, so they could feed off the negative emotions that the villagers produced, using the circus to draw more victims into their trap. Upon mesmerising the dwarf, the Doctor found out that Antonio had come into contact with the Hornets as a young boy, in Venice, 1768 when they came out of a blue box that had appeared from nowhere. Since then he had set up the circus to draw in more victims for the Hornets, and has remained their central hive ever since. However, after the Doctor had extracted all the information he wanted from Antonio, the Hornets had completely left his body, leaving him a husk, with the intent of making Francesca their new hive. The Doctor attempted to stop the Hornets occupying Francesca, but was unsuccessful, leading Francesca to cast herself off the high wire, upon the command of her masters, killing her. After the Doctor's defeat of the Hornets in Blandford, the Doctor had taken the husk of Antonio back to Nest Cottage, and placed a stasis field around it, and then used him as a garden gnome. The Doctor found out that the Hornets remained dormant in Francesca's dead body, which was stolen by Farrow and Sally, presumably at the Hornets command. Eventually, her mummified feet and ballet shoes would make their way to the museum in Cromer. (AG: The Circus of Doom)

The Doctor finally found the earliest infestation of the Hornets in the year 1039, in a nunnery in Northumbria, which was under siege by wild dogs. Here, the Hornets met the Doctor for the first time (from their perspective). While there, the Doctor discovered that the Hornets had recently come to Earth, and were now looking for their lost Hornet Queen who had hidden in the body of a pig trapped in the nunnery. The Hornets took the possession of wild dogs in order to recapture their queen. They eventually achieved this and attempted to escape in the leading dog of the pack, but the Doctor tried to trap the Hornets in his TARDIS. While the Doctor was trying to retrieve the Hornets in the TARDIS, he eventually managed to confront them. Where he realised that they were unable to take possession of the nuns in Northumbria, because they couldn't inhabit the bodies of those who had consumed alcohol. Where the Doctor understood how the Hornets were able to take control of Antonio, Francesca, Ernestina, Mrs Wibbsey and Percy Noggins, who were all teetotalers. Also, the Hornets informed the Doctor that they came to Earth by travelling through the dark vacuum of space, explaining how the Hornets in Nest Cottage were nocturnal, having an affinity with the darkness. The Hornets had managed to take possession of the Doctor, and piloted the TARDIS back to Earth, where they could escape. They escaped and encountered the younger Antonio in 1768. The Doctor searched for the Hornets in Venice for days, but he later realised that he was responsible for the Hornets contact with Antonio, who would eventually set up his Circus of Delights. The Doctor then took the wild dog back to Nest Cottage, where it became his dog Captain. (AG: A Sting in the Tale)

The Doctor put an advertisement in a magazine to invite Mike Yates into his investigation of these Hornets, during this time with Mike Yates, he mentioned his "recent escapades", including "giant rats", "killer robots" and "skulls from the dawn of time". After the stuffed animals in the Nest Cottage came alive and both Mike and the Doctor were forced to retreat into the cellar, the Doctor decided to keep him up to speed, by telling him about all his encounters with the Hornets. (AG: The Stuff of Nightmares) However, the Doctor later claimed that he couldn't remember putting the advertisement in the magazine. (AG: A Sting in the Tale)

The Doctor wanted to finally defeat the Hornets by neutralising their queen. Therefore, with the help of Mike Yates and Mrs Wibbsey, he used Francesca's ballet shoes and his TARDIS's dimensional stabiliser to shrink themselves, so they were able to enter the hive of the Hornets, which happened to be a stuffed zebra housing the Hornet Queen herself. However, using the dimensional stabiliser to shrink themselves would result in the force shield around Nest Cottage being deactivated, allowing the Hornets to be released. During the expedition into the hive of the Hornets, Mike had become paranoid and suspicious of Mrs Wibbsey, leading to his handcuffing her, and directing her to the centre of the hive, in the brain, resulting in a confrontation with the Hornet Queen. It was during this confrontation, the Hornet Queen revealed she had taken possession of Mike, feeding off the negative emotions he felt in his life as a result of his breakdown and his betrayal of UNIT during the Golden Age incident as a means of taking control of his mind. It was this revelation that the Doctor realised that it must have been the control of the Hornets that forced him to put that advertisement in the magazine, using what knowledge she had taken from the Doctor's mind. So she could draw Mike to Nest Cottage, believing him perfect to take control, since he had so many negative experiences as a result of his time with UNIT. Since the Hornets were no longer restrained by the force shield, they all took their opportunity to return to the hive of the Hornets, so the Doctor threatened all the Hornets by burning the whole hive, however, the Doctor realised that he could use the Hornet Queen's desire for the Hornet's royal jelly that they produced, against her. He achieved this by filling Francesca's ballet shoe with royal jelly, and the Queen overcome with the desire for the jelly, drank it out of the shoe. Then, using the residual energy of the Hornets in the shoe, and the sonic screwdriver's connection to the dimensional stabiliser to shrink the Hornet Queen so small she could only exist in the micro-universe. This weakened the Hornets and gave the Doctor the opportunity to escape, so he could increase their size again. Allowing the Doctor to reactivate the dimensional stabiliser, so he could put a force shield around the hive to contain all the Hornets in the stuffed zebra, sending them to the other side of the universe. This gave the occupants of Nest Cottage the chance to celebrate Christmas, the following day. (AG: Hive of Horror)

Traps for the Doctor
One year following the battle with the Hornets, the Doctor returned to Nest Cottage to celebrate Christmas with Mrs Wibbsey, Mike Yates and Captain, (whom the Doctor gave to Mike to look after once the Hornets had been defeated, because he already had a dog aboard the TARDIS and he didn't think the two would get along). While he stayed in Nest Cottage, someone stole the Doctor's spatial geometer, leaving behind a bag with five objects as clues. The first one, the tile from a Roman mosaic, led the Doctor to Celtic Britain. They were taken by Celtic soldiers who believed them to be Druids, and wanted to use them to assassinate the wizard in a neighbouring village, who was threatening them. They travelled to this village, where the Roman Emperor Claudius was posing as the wizard, who desired to escape from Rome and the troubles of being Emperor. During an attack by the Celts from the village, the Doctor managed to stop them from fighting, by using a voicemail message of Mike Yates from the Nest Cottage telephone he had with him. After the battle ended, Claudius attempted to usher the Doctor inside the back reaches of his tent, but failed, and the Doctor escaped before the tent vanished. But not before removing the remains of his spatial geometer that Claudius had taken. (AG: The Relics of Time)

Next, the Doctor found an altered version of a poster painted by Henri de Toulouse-Lautrec. This led the Doctor to Paris in the 1890s where Lautrec's concierge had tried to frame Lautrec as a murderer of street girls, by making him doubt his own sanity. To do this, she slashed his paintings and killed Henri's muses and models, and stored their remains in his house, unbeknownst to him. With the help of Henri's muse, La Charlotte, they discovered the bodies and uncovered the truth of Henri's innocents. From this revelation, they found out that the murders were due to the action of Lautrec's concierge, in part to cover up his need to feed on those girls. In an attempt to lure the Doctor, the concierge kidnapped Lautrec and took him to a cemetery, where her dematerialisation chamber was. The concierge almost captured the Doctor in his time craft, but the Doctor forced his way out, however, La Charlotte was killed before they all could escape. The Doctor then retrieved an other part of his spatial geometer that was left behind. (AG: The Demon of Paris)

The third object - a storybook with images of the Doctor and Mike Yates in it - drew them to a cave in eastern Europe, where he met a story teller, Albert Tiermann on his way to tell his stories to the king. But the materialisation of his TARDIS caused a blockage in the road on his route to the king. They were all forced to remain in a near by hotel owned by Frau Herz until the morning. Albert had discovered the Doctor's copy of Albert's storybook, containing stories he hadn't written yet. Since he was suffering from mental block, and had to tell a new story to the king on pain of death, he had a desire to obtain the book. That night, an Ice Queen whom Albert had previously met in his childhood visited him, and further persuaded him to take the storybook. The following morning, Albert's coachman had been killed, and in an attempt to take Frau Herz hostage, the Ice Queen killed Hans, Albert's footman. The Doctor pursued the Ice Queen to a cave nearby, and found where Albert revealed that all his stories were created for him by the Ice Queen, in her elaborate plan to lure the Doctor here. The Ice Queen returned to the hotel, and threatened to kill Mike. It was now revealed that the hotel was really the dematerialisation chamber, and was in disguise for 40 years, unbeknownst to Frau, all for this moment. Direct threats from the Ice Queen to Mike did not hold the Doctor, so he tricked the Ice Queen into believing he was going to accompany her, allowing Mike, Albert and Frau to escape. Then, at the last minute, the Doctor escaped, leaving the Ice Queen empty-handed. But Mike had discovered more of the spatial geometer in the draws of the hotel. The Doctor deposited Albert and Frau near the king's palace, and allowed Albert to keep the storybook, and used it to write his stories in the future. (AG: A Shard of Ice)

The Doctor ran into a trap in New York City in 1976. A meteorite landed in Central Park and bestowed super-powers to local resident Alice Trefusis. The Doctor investigated the comic book cover showing the event. An ageing film star Mimsy Loyne used a telepath debilitator to confuse him. Mimsy captured the Doctor, but was foiled when Alice broke up the chanting cultists necessary for the debilitator. In frustration, Mimsy kidnapped the Doctor's companion, Fenella Wibbsey, outright. (AG: Starfall)

Following the last item - a golden heart pendant - the Doctor went straight to Sepulchre. The Demon, no longer needing any disguises, sprang the trap on the Doctor. He revealed he was actually working for Mrs Wibbsey, or rather, the Hornets that had regenerated inside of her. The Demon locked the Doctor in a sarcophagus, and started the process to extract all of knowledge of space and time from the Doctor's mind, using it to create the Atlas of All Time for the Hornets. A quick turnabout by Mike Yates set Mrs Wibbsey in the sarcophagus instead, quickly destroying the Hornets, the Atlas and Sepulchre. The Doctor, Mike, and Mrs Wibbsey escaped in one direction while the Demon escaped in another direction, free to roam the universe. (AG: Sepulchre)

Quest for the Key to Time
For this purpose, the White Guardian introduced him to a new companion, Romana. Despite not being to fond of each other, they managed to find the first piece to the Key, which was disguised as a piece of Jethrik that two con artist were using in their schemes. (DW: The Ribos Operation)

While the Doctor and Romana searched for the Key, they were twice interrupted by outside sources emitting chronometric radiation that disrupted the tracer's ability to work, in the form of a chronometric pulse caused by a breach in the higher dimensions (PDA: Tomb of Valdemar) and a network of spatial teleportation paths created by a malfunctioning time cabinet intersecting with Earth's ley lines. (MA: The Shadow of Weng-Chiang) After these two encounters, the Doctor and Romana took a long break from searching for the Key. (PDA: Heart of TARDIS)

During this break, the Doctor, Romana, and K9 encountered a frog-like being named Bolog, who had a fleet of ships at his command, hidden on the far side of the moon.. The Doctor was able to stop him by sending his ships into orbit around the sun with a banana. (DWM: Death to the Doctor!)

Later, the Time Lords contacted him, telling him that they needed him to go on a mission. The Doctor, however, left them after relearning that the Brigadier was in danger, after he was captured by a terrorist group. The Doctor discovered an Avatar universe that had the Second Doctor, Jamie McCrimmon, and Victoria Waterfield trapped inside. Afterwards, they were forced to continue with the quest. (PDA: Heart of TARDIS)

They next tried finding a piece to the Key, but ended up on a planet ruled by a pirate called Captain. The Doctor was caught in the middle of a revolution between the pirates that ruled the planet and the psychically gifted populace that grew in number each time the planet materialized over another for riches and resources. Defeating the Captain and his nurse, the real master mind, the Doctor revealed to Romana that one of the planets that was being held as a miniaturized trophy was the second piece. (DW: The Pirate Planet)

He next journeyed to Boscombe Moor, where he found the third piece as the necklace belonging to the intergalactic criminal Cessair of Diplos, who had been posing as an ordinary Earth woman while her thick-headed jailers where captive in hyperspace. The Doctor outwitted both foes and obtained the third piece. (DW: The Stones of Blood)

When looking for the fourth piece, the Doctor decided to take a relaxing fishing break while Romana went to look for it. Though successful in finding the piece to the Key, they both were forced into the political power struggle on Tara. In the end, the Doctor was able to help expose the vile Count Grendel for using deception to claim the throne before his cousin. (DW: The Androids of Tara)

The search for the fifth piece brought the Doctor and Romana to Delta III where the Swampies worshipped an overgrown squid called Kroll. Putting himself in harm's way, the Doctor found Kroll had swallowed the piece to the Key and was transformed by its properties. Reclaiming the piece, he and Romana returned to search for the last one. (DW" The Power of Kroll)

Searching for the final piece brought the Doctor and Romana to a war-torn planet being attacked by a computer planet near by. There, they met the Shadow, an agent of the Black Guardian, who was also after the Key. Unfortunately, the final piece was in the form of a living being - Princess Astra. Regrettably, the Doctor completed the Key and quickly separated it back into it originals components. To avoid the wrath of the Black Guardian, the Doctor used the Key to instal a randomiser in the TARDIS to prevent himself or the being from knowing where he would go in time. (DW: The Armageddon Factor)

Romana II
While repairing k-9, the Doctor found Romana had regenerated into Astra's form, much to his displeasure. They landed on Skaro, where the Daleks were excavating the remains of the Kaled base for the restored Davros. The Doctor also faced an android race that was at war with the Daleks; they both needed someone to reprogram their computers for "illogical" movements that would give either side an advantage. (DW: Destiny of the Daleks)

Forgetting Romana was only to be with him for the quest for the Key, the Doctor decided to bypass the randomiser and take himself and Romana on a relaxing holiday to Paris in 1979. There, the Doctor discovered that a Jagaroth named Scaroth had been splintered into twelve selves throughout time after his spaceship exploded, which led to the creation of life on Earth through the radiation from the exploding ship that affected the primordial ooze. The Doctor, Romana and detective Duggan succeeded in stopping Scaroth from preventing his spaceship from exploding, which would have undone life on Earth. (DW: City of Death)

The Doctor later received a distress signal and arrived on Chloris, a lush and verdant world with only small quantities of metals, all of which were controlled by its ruler, Lady Adrasta. The Doctor was sent for execution, but managed to avoid it, deciding to investigate the creature he was supposed to be fed to. He found it to be an imprisoned Tythonian that had been sent by its people to set up a trade agreement with Chloris. Deciding to end Adastra's tyranny, the Doctor allowed the Tythonian to kill her and let a new reign of peace be set up between the two species of the planet. (DW: The Creature from the Pit)

The TARDIS then arrived on the space liner Empress, which had become locked together with a private ship, the Hecate, after colliding with it upon emerging from hyperspace. The Doctor and Romana met Tryst, who had a Continuous Event Transmuter machine. However, some Mandrels from Eden had somehow gotten onboard. The Doctor later discovered he had been lied to and the supposed addictive drug vraxoin was actually a valuable material that the Mandrels decomposed into. The Doctor thwarted the plan of Tryst and the pilot of the Hecate, separated the two ships, and returned the Mandrels to Eden. (DW: Nightmare of Eden)

Whilst in the middle of conducting TARDIS repair, the Doctor and Romana were caught in the middle of a sacrificial ceremony for a "god" called the Nimon. They discovered that this "god" was actually a parasite alien preparing Skonnos for the rest of its species. The Doctor succeeded in preventing the teleport from bringing more than two extra Nimon before the Nimon killed themselves as an accidental side-effect to their final gambit. With the help of the Anethans originally sent to be life-force sacrifices for the transporter, the Doctor destroyed the remaining Nimon before departing with Romana. (DW: The Horns of Nimon)

While travelling with Romana and K9, the Doctor receives a message from Professor Chronotis, who was living at St Cedd's College in Cambridge. During this encounter the Doctor met Chris Parsons and Clare Keightley, who helped him to fight Skagra. Skagra attempted to steal The Worshipful and Ancient Law of Gallifrey so he could break into Shada and retrieve Salyavin from his imprisonment. Without realising that Salyavin had escaped, and living under the alias Chronotis, the Doctor had to foil Skagra's plot, which involved taking Salyavin's power to project his mind into other minds, so he could use it to shift his mind into the minds of all life in the universe, using his Krargs. After defeating Skagra, the Doctor imprisoned him in his own ship, and decided to allow Salyavin to remain on Earth. (DW: Shada) However, these events might've been negated, due to Borusa attempting to remove the Doctor from time using the time scoop. (DW: The Five Doctors) This might have forced the Eighth Doctor to reenact these events with Romana and K9 in the future. (BFA: Shada)
 * The Doctor, Romana and K9 Mark II spent an indeterminate period of time together, potentially quite a lengthy one given the Doctor and Romana's long life spans as Time Lords.

Tired of his constant unknown travels, the Doctor took a break in Brighton Beach, but landed in the wrong season to do so. At Romana's urging for a technologically advanced place of relaxation, the Doctor took them to the Leisure Hive, where the remaining Argolins ran it. However, during the adventure to repair a rejuvenation machine, the Doctor ended up ageing hundreds of years. A genetically created Argolin named Pangol decided to take over, but thanks to the Doctor's interference, his plan to create a clone army of himself backfired as the Doctor was in the machine beforehand, gaining his youth back. However, the Doctor had to remove the randomiser in order to repair the machine, deciding that he had enough of running. (DW: The Leisure Hive)

Arriving on Tigella after repairing K9 from their previous adventure/vacation, the Doctor and Romana found themselves trapped onboard the TARDIS in a time loop by the last of the Zolfa-Thurans, Meglos, who also took the Doctor's form after attaching itself to a humanoid body to help itself steal the power of Dodecahedron. However, the Doctor was successful in redirecting the death beam Meglos had pointed at Tigella back on him after escaping the time loop. (DW: Meglos)

Travels in E-Space
While trying to return to Gallifrey to take Romana back and reunite with Leela, the Doctor was taken by surprise when the TARDIS entered a pocket universe called E-Space. During this time, the Doctor picked up a new companion, Adric, who was nearly just as intelligent as he was. (DW: Full Circle) The Doctor eventually found a way to leave E-Space through a new opening at zero coordinates, but to his displeasure, Romana chose to stay behind to help liberate enslaved Tharils with K9. (DW: Warriors' Gate)

Back home
Following his return from E-space with Adric, the Doctor was in an increasingly morose and dark mood due to missing Romana. He was called by the Traken Union's Keeper to assist him in keeping evil away while his power waned from age and a replacement Keeper was found. The Doctor was successful in preventing the still decaying Master from obtaining ownership of the Source, but was unable to prevent him from stealing the body of Councillor Tremas. (DW: The Keeper of Traken)

Tired of the TARDIS' chameleon circuit being stuck as the police box, the Doctor decided to measure one and give the numbers to the people on Logopolis to fix it. However, he was impeded in his task by the newly reborn Master and was temporarily shrunk down along with the TARDIS due to a mathematical error. However, this error was quickly rectified and the TARDIS was reborn, minus the still malfuctioning chameleon circuit. During the fight, he picked up two additional companions, Tegan Jovanka and Nyssa. Much to the Doctor's horror, the Master had stopped all computations on Logopolis for too long; the universe had needed Logopolis to survive past its natural end and CVEs were the only thing allowing the universe to continue. The Doctor decided to form a shaky alliance with the Master to use the Pharos Project Radio to open a new CVE and save the universe. (DW: Logopolis)

Death
Despite having saved the universe, the Doctor knew the Master would try to make the situation work for him and was correct when he found the Master was going to blackmail the universe into servitude in exchange for its continued existence. Successful in making the CVE permanently open, the Doctor fell from the Pharos Project radio telescope to the ground, hundreds of feet below, after disconnecting a wire. Though his companions were greatly worried about him, the Doctor told them the moment had been prepared for. The Watcher, which had been tracking him through time and space and was an apparition of his next incarnation, merged with him and the Doctor regenerated.

Undated adventures

 * The Fourth Doctor and Azmael had an encounter in which Azmael drank so much that the Doctor had to throw him into a pool to sober him. (DW: The Twin Dilemma)
 * The Fourth Doctor attended the funeral of Alistair Gordon Lethbridge-Stewart. (ST: The Gift)
 * River Song met the Fourth Doctor, writing in her diary that he had a whole room just for his scarves. She wiped his memory with mnemosine recall-wipe vapour so their personal timelines wouldn't be contaminated. (VG: The Eternity Clock)

Age

 * While on Earth, the Doctor stated his age to be 749 years. (DW: The Seeds of Doom)
 * After ageing four years from crossing a split in time, the Doctor said: "I shall still think of myself as 743 ... or was it 730, I never can remember..." (DWM: The Time Witch)
 * See separate article.

Personality
The Doctor's fourth incarnation was most definitely not human-like in nature, and he stood apart from others, even most of his own people. (DW: The Deadly Assassin, The Invasion of Time)

The Doctor was known to be aggressive as when the Krynoid pods came to Earth (DW: The Seeds of Doom)

When Sarah upbraided him over his callousness at the sight of Laurence Scarman killed by the animated corpse of his own brother, the Doctor reminded her of the larger issue of stopping Sutekh. (DW: Pyramids of Mars) His mind often leapt ahead of anyone, including himself. He delighted in keeping both friends and foes alike off guard with oddball humour and curious pranks, as in his second incarnation. Although generally peace-loving and kind-hearted, as were most of his incarnations, the Doctor could also react with sudden violence when necessary. He was also not against taking a life in extreme circumstances, (DW: The Brain of Morbius, The Ribos Operation) but in their first adventure, scolded Leela multiple times for unnecessary killing. (DW: The Face of Evil)

He told the mutating Sorenson that the results of his experiments were his own fault and took no action to help him and proceeded to throw him into the pool of anti-matter. He did however rescue Sorenson when the process was reversed. (DW: Planet of Evil)

He could judge character keenly, almost instantly knowing whom to trust or seeing through Unstoffe's false guilelessness. (DW: The Ribos Operation) Of all of the Doctor's incarnations, this one had perhaps the most consistently anti-authoritarian attitude, with little tolerance for religious dogma. (DW: The Brain of Morbius, Underworld, The Stones of Blood, The Power of Kroll) or nationalism. (DW: Robot, The Armageddon Factor) The Doctor often played the fool to lull his opponents, such as Count Scarlioni, into underestimating him, though it did not work in Count Scarlioni's specific case. (DW: City of Death)

Despite his charm and offbeat humour, the fourth incarnation was arguably more aloof and sombre than his previous incarnations. He could be intensely brooding, serious and even callous, and would keenly scrutinise his surroundings even when playing the fool. He would be furious with those he saw as stupid, frivolous, misguided or evil. When taking charge, he could be considered authoritative to the point of egocentricity, but he was usually the only one capable of solving the situations he found himself in. He generally maintained his distance from the Time Lords, even after they had lifted his exile, and resented that they were capable of re-entering his life when they deemed it necessary. Not only did he seem more inclined toward a solitary existence, (DW: The Deadly Assassin) he also emphasised his distance from humanity, although he stated on more than one occasion that he found mankind to be his favourite species. (DW: The Ark in Space)

Unlike his third incarnation, this incarnation did not have a close working relationship with UNIT or the Brigadier, reacting with anger when UNIT recalled him to Earth. (DW: Terror of the Zygons) Except for this and a handful of other occasions, the Doctor kept his distance from UNIT, even at the expense of abandoning his predecessor's beloved roadster, Bessie. Later incarnations never re-established the same rapport that existed between the Doctor and UNIT before his fourth incarnation, although his tenth incarnation assisted UNIT a few times. (DW: The Sontaran Stratagem/The Poison Sky, Planet of the Dead)

As the youngest-appearing incarnation at the time, the Doctor found himself drawing closer to some of his companions than he might have previously, in particular, with Sarah Jane Smith, who it was later implied, though never stated, may have fallen in love with him. (DW: School Reunion) If any of his other female companions felt the same way, the Doctor, through intent or quirk of personality, did not appear to notice. He tended not to display such feelings himself, not even when accompanied by the often scantily clad Leela, although during one adventure he acknowledged the fact that Romana was attractive, (DW: The Pirate Planet) and in another adventure he even kissed her. (MA: The Well-Mannered War) He was more likely to make remarks such as telling Countess Scarlioni, "You're a beautiful woman ... probably". (DW: City of Death)

Habits and Quirks
Souvenirs from many different worlds littered the fourth incarnation's pockets. (DW: Robot, Genesis of the Daleks) He would sometimes relax by playing with a yo-yo and liked to drink ginger beer. (DW: The Android Invasion)

He would often have jelly babies with him and offer them as a greeting. While past and future incarnations also showed occasional fondness for the sweet, it was never as frequent as this incarnation's love for them. In his later life he developed a great fondness for tinkering about in his TARDIS. He relied upon his sonic screwdriver at least as much as in his previous incarnation.

He was also not adverse to winding up his companions on occasion, such as once fooling Leela into standing and playing with a yo-yo for an extended period of time, with her believing it was an experiment. (DW: The Robots of Death) On another occasion, he caused Romana to nearly panic when he pretended to become possessed by the Black Guardian. (DW: The Armageddon Factor)

Another habit he had was giving a K9 robot to his departing female companions. When Sarah Jane left, he gave her K9 Mark III. (KAC: A Girl's Best Friend) When Leela stayed on Gallifrey, he gave her K9 Mark I. Lastly, he gave Romana K9 Mark II when she decided to stay in E-Space. (DW: Warriors' Gate)

Appearance
In stark contrast to the elegant and refined, but somewhat flamboyant, figure of his third incarnation, the fourth incarnation was an unkempt, awkward-looking figure, dressed in battered clothing and a ridiculously long, multi-coloured scarf, which had originally been knitted for him by Madame Nostradamus. (DW: The Ark in Space) His dark curly hair was often partially hidden by a large floppy hat. Professor Marius remarked that the Doctor looked like a "space vagrant". (DW: The Invisible Enemy) The fourth incarnation was also notable for being the first incarnation to wear clothing with question mark motifs. The same was later true of his fifth, sixth and seventh incarnations. (DW: The Leisure Hive, Castrovalva, The Twin Dilemma, Time and the Rani, et al.)

His costume changed throughout his life. His initial costume consisted of a red-brown blazer with elbow patches, baggy grey tweed trousers, a dark brown cardigan with diamond shapes adorning the front, a white dress shirt and a long green neck-tie. (DW: Robot - Revenge of the Cybermen) It changed slightly with a different scarf and hat (DW: Terror of the Zygons) and again with the original scarf, albeit a different waistcoat, shirt and cravat. (DW: Planet of Evil) Eventually, the basic style stabilised with a frock coat and some form of a cravat or tie with the above mentioned articles of clothing. (DW: The Android Invasion) He wore several frock coats of different colours, including a dark brown one, (DW: Pyramids of Mars) a light grey one, (DW: The Brain of Morbius) and a light brown one.

Throughout his life, his costume alternated with different shirts, cravats, frock coats, waistcoats and other various pieces of clothing until he later settled on one outfit consisting of an open-neck shirt, an unbuttoned waistcoat, a tan frock coat, knee-high leather boots, trousers and of course the famous scarf. (DW: The Power of Kroll) He wore this costume alternating between ankle-high leather shoes and the boots. (DW: City of Death, et al.) From his second attempt to reach Brighton Pavilion, however, his costume changed dramatically, with a red and maroon colour scheme. This consisted of a full-length maroon coat, waistcoat, trousers, buccaneer-style leather boots, a Poet's Hat, a white open-neck dress shirt with question marks adorning the collars (a trait that continued through to his fifth, sixth and seventh incarnations) and a new scarf. (DW: The Leisure Hive) This scarf was longer than his previous scarves; when it was looped around his neck, the loop reached the floor, and so did the ends. He adopted a maroon, red and purple colour scheme to match the rest of his clothes. He continued to wear this until the end of his life. (DW: Logopolis) His costume regenerated slightly when he did, as seen by the Fifth Doctor's ankle-high golf shoes and pulled-up socks instead of the leather boots. (DW: Castrovalva) The Doctor had kept parts of his costume throughout the years. (DW: Time and the Rani, The Christmas Invasion)

Like several of his later incarnations, his pockets were dimensionally transcendental. The array of items he carried included:
 * a seemingly endless supply of Jelly babies
 * a galactic passport (DW: Robot)
 * a cricket ball (DW: The Ark in Space, The Hand of Fear)
 * a yo-yo, which, with a sheepish grin, he would explain was useful for taking gravity readings (DW: The Ark in Space)
 * a selection of books, including his 500 Year Diary, (DW: The Sontaran Experiment) Oolon Caluphid's Origins of the Universe and a Tibetan language handbook (DW: The Creature from the Pit)
 * a magnifying glass, gemstones, handcuffs, and an etheric beam locator which also detected ion-charged emissions (DW: Genesis of the Daleks)
 * a lockpick (DW: Pyramids of Mars).
 * a football rattle
 * a magician's cane (DW: The Hand of Fear)
 * a clockwork egg-timer (DW: The Face of Evil)
 * a breathing tube, a barrister's wig, and an instant camera (DW: City of Death)
 * On one occasion, he even dropped a cup containing a hot beverage into his pocket. (DW: The Power of Kroll)

Casting
Actors considered for the role of the fourth incarnation included Michael Bentine, Bernard Cribbins, Graham Crowden, Fulton Mackay and Jim Dale. Tom Baker was cast based on his role as the villain Koura in.

Appearance
According to the creators of the show and Baker, the character's look was originally based on paintings and posters by Henri de Toulouse-Lautrec of his friend, Aristide Bruant, a singer and nightclub owner whose trademark was a black cloak and long red scarf.

Possible romances
Since the fourth incarnation was the youngest in appearance at the time, he therefore appeared closer in age to his companions. This led to concerns being expressed of possible "hanky panky in the TARDIS", a term often used in the tabloid press to suggest the impression of off-screen dalliances between the various Doctors and their young, female companions.

Perhaps to address this, according to the Information Text commentary on the 2007 DVD release of The Stones of Blood, Baker generally tried to emphasise the asexuality of the character, apart from possible subtle romantic tension such as that with Sarah Jane Smith. Despite this, Baker was not above tossing in occasional visual jokes that suggested sexual tension. For example, in The Stones of Blood the Doctor and Romana have to huddle close in order to be within the confines of a transporter beam and enter what would, in normal circumstances, be seen as a romantic clinch, but neither character appears to recognise this. Likewise, the Doctor and Romana are forced into close proximity in The Ribos Operation when hiding from Graff Vynda-K and neither seem to recognise this as a romantic moment.

In popular culture
The fourth incarnation's distinctive appearance and mannerisms have made him a target for affectionate parody. The character appeared several times on The Simpsons and twice on. Even in 2011, a full 30 years after he left his tenure as the Doctor, an animated parody of his incarnation appeared an episode of. In Hugo 2: Whodunnit?, a computer game, the player's character can save Tom Baker's Doctor from a Dalek, who in return gives the player his sonic screwdriver.

He is frequently impersonated by impressionist Jon Culshaw on the radio and television series. Even had an episode featuring an eccentric man claiming to be a time-traveller and wearing a long striped scarf. Archival footage of the fourth incarnation's first title sequence was also used in the episode "Blue Harvest" to represent and parody Star Wars's hyperspace.

Tom Baker, as the narrator of the series, has referenced Doctor Who. He also appeared in Doctor Who and the Daleks in The Seven Keys to Doomsday, a stage play that opened two weeks before Baker began his tenure as the Doctor. In the play, Trevor Martin plays an alternative version of the fourth incarnation.

In the book, there is a scene in which a bunny sits on top of the TARDIS with a noose around its neck as the fourth incarnation runs into it, being chased by a Dalek.

wore a costume similar to the fourth incarnation's when he played Derek in his film Bad Taste.

On, in the episode, "The Justice League Recombination", Stuart wears the Fourth Doctor's costume to a New Year's Eve costume party at his comic book shop.

Reprising the role
Unlike his predecessor Jon Pertwee and his successors Peter Davison, Colin Baker, Sylvester McCoy and Paul McGann, Tom Baker was notoriously hesitant to reprise the role of the Doctor. Originally intended as a major player in the 20th-anniversary special, DW: The Five Doctors, Baker pulled out before production began, citing other obligations as his reasoning. The production team rewrote the scripts to give much of his role to the Fifth Doctor, and included the Fourth Doctor by making use of unbroadcast footage from DW: Shada. A Madame Tussauds wax mannequin of his incarnation was used in publicity shots to keep the "five Doctors" concept afloat.

In 1993, Baker agreed to reprise the role for the opening scenes of the charity special DW: Dimensions in Time, but the fourth incarnation did not otherwise interact with any of the other incarnations or companions in the piece. Baker had also considered playing the Doctor again for a 30th anniversary special, The Dark Dimension, which was cancelled before filming began. Around this time, he also introduced a VHS reconstruction of Shada, though not apparently in character as the Doctor. In 1997 he returned to the role in a more serious manner in the video game Destiny of the Doctors.

Despite his hesitancy to play the role again, Baker made frequent appearances on DVD releases of his stories, recording audio commentaries for many and conducting on-camera interviews for others.

In the 2000s, Baker made a tentative step towards reprising the role by agreeing to record audio books for BBC Audio, reading the texts from several Target novelisations from his era. Finally, in 2009, Baker agreed to return to the role of the Doctor in a dramatic context, performing the five-part AG: Hornets' Nest story arc, again for BBC Audio, in which he was paired up with Richard Franklin, reprising the Pertwee-era companion Mike Yates.

In March 2010, Baker announced on his official website that he was in discussions with Big Finish Productions to record Doctor Who audio dramas for the company. . Big Finish confirmed this on 3rd June 2010. A few days later it was also confirmed that Baker would be doing additional stories for BBC Audio, AG: Demon Quest, released at end of 2010.

The Brilliant Book
According to The Brilliant Book 2011, a non-narrative source, the Fourth Doctor met Winston Churchill in 1879, posing as a Punch and Judy man  whilst hunting Cybermats.