Harry Sullivan

Surgeon Lieutenant Harry Sullivan, a Royal Navy surgeon in the employ of UNIT, was also for a time, the companion of the Doctor. He later worked for NATO and MI5.

Relatives
Harry had a brother named Will, whom Sarah Jane Smith would meet later. (BFSJS: Buried Secrets) Will would later die shortly after meeting her. (BFSJS: Fatal Consequences)

Career with UNIT
He first encountered UNIT while working in the Royal Navy, during which time the Doctor had briefly left Earth in the TARDIS (PDA: The Face of the Enemy, referencing The Curse of Peladon).

Later, after he had joined UNIT and the Doctor apparently in a pre-regenerative coma, the Brigadier summoned "Dr Sullivan" to help see him through the process. Sergeant Benton, however, woke the Doctor by offering him a cup of coffee. The Brigadier then told him not to bother. (DW: Planet of the Spiders)

After confronting the Great One on the planet Metebelis III, the Doctor then disappeared. The Brigadier believed he had died until after some months, the TARDIS re-appeared in his laboratory at UNIT HQ. The Doctor had received a near-fatal dose of radiation and would have to either regenerate or die. (DW: Planet of the Spiders) Harry Sulivan arrived on the scene just moments after the Doctor regenerated into a new form (DW: Robot)

Adventures with the Doctor
Harry Sullivan, at very first much confused by the Doctor, trailed him and his companion Sarah. After the defeat of the robot K1, Harry found himself in the Doctor's TARDIS with them. (DW: Robot) The three found themselves first on Space Station Nerva pitted against Wirrn (DW: The Ark in Space) and then by transmat from the space station travelled to an uninhabited far future Earth in the same time period facing up to the Sontaran Styre. (DW: The Sontaran Experiment) The transmat then took them not back to Space Station Nerva, where they had left the TARDIS, but to Skaro during the time of the creation of the Daleks on a mission given to them by the Time Lords (DW: Genesis of the Daleks) Via time ring, they traveled back to Nerva, but the time ring had transported them to a much earlier time period. (DW: Revenge of the Cybermen)

Back in the late 20th century, Harry joined up with UNIT again to defeat the shape-changing Zygons and their giant dinosaur-like beast, the Skarasen in Scotland. The Zygons captured Zygon and one assumed his form. He decided to go home to London by train rather than by TARDIS. (DW: Terror of the Zygons )

A short time later, Harry helped the Doctor against the Kraals. (DW: The Android Invasion)

Post-UNIT career
In the early 1980s, Harry went to work at NATO. (DW: Mawdryn Undead, TCDW: Harry Sullivan's War) By 1997 he had gone on a post as Deputy Director at MI5. At that time, via the agency of time travel, he met up once again with a familiar version of the Doctor, as well as a much younger Sarah Jane Smith, for whose personal timeline, little time had passed (MA: System Shock). He still worked for MI5 in 1999. (PDA: Millennium Shock).

Circa the 2000s, he worked for NATO, having achieved the rank of Commodore. The Brigadier, at this time, asked him for a favour. (U.N.I.T.: The Wasting)

Alternative timelines
A parallel Earth version of Harry serving on a nuclear submarine in a dystopian world ruled by the Silurians. He managed to save the life of the the Doctor's companion Bernice Summerfield. (NA: Blood Heat)

Personality
Harry was rather old-fashioned and stereotypically English in his attitudes. He often employed slightly archaic language for example, referring to Sarah affectionately as "old girl" or "old thing". (DW: The Sontaran Experiment) He was nonetheless depicted as possessing great bravery and a "can-do" attitude, adapting well to the many strange situations in which he found himself. He could, however, also be quite clumsy and unsubtle, leading the Doctor to once declare, in a moment of frustration, that "Harry Sullivan is an imbecile!" (DW: Revenge of the Cybermen) Nonetheless he had has a slightly flirtatious relationship with Sarah.

Behind the scenes
Harry was written in as a companion when it was initially thought that the Fourth Doctor would be an older, less physical character. This would neccesitate Harry to handle physical "two fisted" action as the plot required. This was no longer a concern when Tom Baker was cast for the role as he was younger than the previous actors and capable of physical action on his own. Harry was considered redundant and ultimately written out of the show, despite his popularity.

Although various spinoff media have depicted Harry living into the 21st century, in real life the actor who portrayed him, Ian Marter, died in 1986. A reference to the character is made in The Sarah Jane Adventures episode Invasion of the Bane when Sarah Jane considers Harry as a possible name for her adopted son, Luke Smith. It has yet to be established whether Harry Sullivan still lives in the present-day continuity of the Doctor Who Universe.

After leaving the cast of Doctor Who, Ian Marter went on to write several Target Books novelisations. He also wrote Harry Sullivan's War for them in 1985. In Harry Sullivan's War, the character has become an MI5 operative. Marter was believed to have been planning a sequel at the time of his tragic death from a diabetic coma the following year.

Marter also wrote the novelisations Doctor Who and the Ark in Space and Doctor Who and the Sontaran Experiment, putting him in the unique position of adapting two stories in which he himself had acted.