Sherlock Holmes is the world's most famous fictional detective. Created by Sir Arthur Conan Doyle in 1887, the iconic character has since appeared in dozens of films and TV shows.
The current BBC series Sherlock, starring Benedict Cumberbatch and Martin Freeman as Holmes and Dr Watson Watson, has become a global phenomenon.
To coincide with the start of the show's fourth series, IBTimes UK has produced a guide to some of the London filming locations seen in the show.
North Gower Street
North Gower Street is the much quieter road that stands in for Baker Street in Sherlock. Flat 187, immediately to the left to the cafe in the above photo, is where Holmes and Watson are seen to reside.
This spot is only used for exterior shots in the show. All interior shots of 221b Baker Street are filmed on a set in Cardiff.
Speedy's Cafe itself has featured in the show. Originally dressed as 'Mrs Hudson's Snax' in the Pilot, interior scenes were filmed inside the cafe in Series Two.
Gerard Street in London's Chinatown featured in Series One episode The Blind Banker, with Sherlock and Watson seen walking past the Feng Shui Inn.
Other Chinatown parts of the episode, including the Lucky Cat Emporium, were actually shot in Newport in Wales.
In the time Sherlock Holmes was written, the capital's Chinese community lived further east in Limehouse. Today's Chinatown was first established in Soho in the 1970s.
This imposing building is used in the show to represent the infamous Diogenes Club, the fictional gentleman's club where Sherlock goes to meet his brother Mycroft. In both the books and the show, talking of any kind is strictly forbidden inside the club.
In real life, it's actually the British Academy in Carlton Terrace, which functions as the UK's national body for the humanities and social sciences.
Some 50 gentlemen's clubs still exist in London today, with a handful still refusing to allow women members.
South Bank Skate Park
Located between the Hungerford Bridge and Waterloo Bridge, every day skaters and bikers venture inside the undercroft of the South Bank Skate Park to practice their skills by the Thames.
The location featured in The Blind Banker, where graffiti artist Raz shows Sherlock and Watson cryptic symbols graffitied on to the walls.
The Skate Park was in danger of being demolished a few years ago under plans to develop the undercroft. But after thousands of planning objections, the skate park was saved in 2014.
St Bartholomew's Hospital
The last location in this guide is one of the most iconic in the show. St Bartholomew's Hospital (commonly referred to as St Bart's), is where Sherlock and Watson first meet in both the book and the show. It is also where Sherlock's friend Molly Hooper works, a new character invented for the BBC adaptation.
But the reason why this particular spot will seem familiar is because this is where the dramatic finale to series two episode The Reichenbach Fall takes place, when Watson witnessed Sherlock seemingly fall to his death from the roof of the hospital.
Of course, it turned out that Sherlock didn't really die, allowing us to continue enjoying the adventures of Sherlock Holmes and John Watson across London.