Sherlock: 221B and London

Army doctor John Watson is back from service in Afghanistan and needs a room; Sherlock Holmes is looking for someone to share the flat at 221B Baker Street, owned by landlady Mrs Hudson. They move in together in the first episode, broadcast in July 2010, and the flat becomes the series' base for everything that follows. The front door the cameras keep returning to is not in Baker Street at all: the exterior shots use a house on North Gower Street, just north of Euston Road, which the BBC itself calls the location for Sherlock's Baker Street.

Visitor guidance: North Gower Street runs just north of Euston Road; the door belongs to a private house, so look from the pavement.

Later in the same episode the hunt for a murderer comes home: tracing the killer's phone through her online account, Sherlock finds its GPS signal at 221B Baker Street, with a taxi waiting for him on the street outside. The address is fiction, but Baker Street has its own 221B: the Sherlock Holmes Museum, opened in 1990, bears the number by permission of the City of Westminster though it stands between numbers 237 and 241. Inside it keeps the years 1881 to 1904, when the stories have Holmes and Watson lodging there as Mrs Hudson's tenants.

Visitor guidance: The museum house lies between numbers 237 and 241 on Baker Street.

John and Sherlock are brought to meet Mycroft inside Buckingham Palace, the monarch's official London residence and administrative headquarters. Mycroft's problem is delicate: the dominatrix Irene Adler holds compromising photographs of a female member of the royal family, stored on her phone. The episode even takes its name from the neighbourhood: Belgravia, the district of London adjoining the palace grounds.

Moriarty announces himself with a triple heist: from his phone he cracks the case where the Crown Jewels are kept, the Bank of England vault and every cell in Pentonville Prison at once. Before smashing the jewel case he writes two words on it for the cameras — Get Sherlock — then lets the police catch him wearing the jewels, seated on the throne. The jewels live, as they long have, in the Tower of London, the home of the Crown Jewels of England.

Cornered, Sherlock turns to the one person he has been kind to: Molly Hooper, the pathologist at Barts Hospital who occasionally assists with his cases. He admits that he respects her and has always trusted her, tells her he is in grave danger, and humbly asks her for help. Then he texts Moriarty to meet him on the hospital roof to settle their final problem. The roof belongs to St Bartholomew's — Barts — a teaching hospital in the City of London founded in 1123 by Rahere.

Two years after his supposed death, Sherlock Holmes is back in London, absolved of everything said against him. He deduces the strike will hit the Houses of Parliament during a late-night anti-terrorism hearing on Guy Fawkes Night, 5 November. Below the streets, he and John enter an abandoned station near Parliament and find the diverted carriage: rigged with explosives into an enormous bomb, defused at the last moment with an off-switch. Above them stands the real Palace of Westminster, meeting place of Parliament, its Elizabeth Tower holding the bell called Big Ben.