107 Baker Street, postcode W1U 65P, (AUDIO: Fugitives) was a house in London owned by the Doctor from at least his fourth incarnation, and used by him and his companions throughout the 19th, 20th and 21st centuries.
The house was multiple stories tall, (AUDIO: The Haunting of Thomas Brewster) and had a secret cellar, which was accessed through a false wall in the larder in the parlour, as well as a priest hole (AUDIO: The White Room) and an attic, (AUDIO: The Haunting of Malkin Place) which boasted its own bedroom. (AUDIO: The White Room) By 1980, it had a television with three channels. (AUDIO: The Movellan Grave)
After the house was left to him in 2008, (AUDIO: A Perfect World) Thomas Brewster subdivided it into five flats. It included a big apartment on the second floor; flat 2 was on the ground floor. (AUDIO: Lost Property)
In 1894, the Sixth Doctor, using the alias "Professor Claudius Dark", told his friends Henry Gordon Jago & Professor George Litefoot to go to the house dressed as the fictional characters Sherlock Holmes and John Watson. There they met the creator of the characters, Arthur Conan Doyle, who had been told where to meet the investigators by "Professor Dark". (AUDIO: The Monstrous Menagerie) During their stay there, they were joined by Ellie Higson, who helped them to defeat Remorse. (AUDIO: The Night of 1000 Stars)
In 1918, Molly O'Sullivan stayed in Baker Street after leaving the front lines. After she left with the Eighth Doctor, Molly gave David Walker the keys to the house. (AUDIO: The White Room) David lived in the house until the 1970s. In the interim, he married a woman named Isabelle and they raised their two sons, one of whom was named Nigel, in the house. (AUDIO: Eyes of the Master)
In the 1920s, River Song stole the Doctor's TARDIS, left at Baker Street by the Fourth Doctor. (AUDIO: Whodunnit?) Indeed, the Eighth Doctor avoided the house during his time in 1921, due to its use by his fourth incarnation (AUDIO: A Life in the Day) after he'd been stranded in 1917 with his TARDIS in 1922. During this time, the Fourth Doctor Romana had been staying in the house, where they'd received cryptic notes from the future Fourth Doctor in the attic. (AUDIO: The Haunting of Malkin Place)
In 1940, the Eighth Doctor parked his TARDIS at the house, because he didn't trust Churchill having access to the TARDIS. Churchill later had himself and Liv Chenka driven to the house, so Liv could contact Heliyon from the TARDIS. (AUDIO: Their Finest Hour)
Due to the interventions of Kotris, (AUDIO: Eyes of the Master) by 1970, the house was the base of the Ides Scientific Institute. In 1972, the Eighth Doctor visited Baker Street. Shortly after the Doctor arrived, a time-space portal opened and Daleks came through, chasing the Doctor, Molly O'Sullivan and Sally Armstrong from the property. (AUDIO: Fugitives) After Kotris was erased from history, the Ides Institute was no longer located in Baker Street.
Following a confrontation with the Master, the Doctor went off alone, leaving Liv Chenka and Molly O'Sullivan to live in the house (AUDIO: Eyes of the Master) in 1972. (AUDIO: Lost Property) One day while living there, Liv helped the alien Lila to escape from Earth. (AUDIO: The World Beyond the Trees) Later, the Master and Sally kidnapped Molly from Baker Street. (AUDIO: Eyes of the Master)
In 2008, the Fifth Doctor, Nyssa, and Thomas Brewster returned to the house, by which time the furniture was falling to pieces and covered in cobwebs. After their stay in London, Brewster decided to stay behind in the city, with the Doctor allowing him to stay in and maintain the house as a parting gift. (AUDIO: A Perfect World) During his time there, Brewster subdivided the house into five flats, with building work done with loans against the property. (AUDIO: Lost Property)
Brewster had vacated it by 2011 (AUDIO: The Crimes of Thomas Brewster, The Feast of Axos) or 2010. (AUDIO: Tales from the Vault) After his departure, the building began to deteriorate, and it stood without an official landlord for almost a decade.
Tania Bell moved into flat 1 in around 2014, (AUDIO: Lost Property) as she worked for Torchwood who were waiting for the Doctor to return to the house. (AUDIO: Must-See TV) Soon after she moved in, Ron Winters and Tony Clare moved into Flat 3. Later, sisters Aisha and Zakia Akhtar moved into flat 2.
In 2020, the Eighth Doctor, Liv Chenka, and Helen Sinclair became stranded in London, and turned up to their house to discover for the first time that it had been subdivided into flats. The Eighth Doctor took up the role of landlord, and moved into the attic, while Helen and Liv moved into flat 4. Around six weeks after the Doctor's arrival, Ken Bright-Thompson and his son Robin Bright-Thompson moved into flat 4. (AUDIO: Lost Property)
Behind the scenes
Though it's possible that a real world location doesn't exist in the same geographic space in the Doctor Who universe, such cases are few and far between. Thus, the map at right is probably a good indicator of the DWU location of 107 Baker Street.