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The game has been seeded virally, - famously the number at which Holmes's fictional residence is located on Baker Street.

One friend takes the role of Holmes and the other is his sidekick Dr Watson. Together they chase villains, interact with characters from the movie, working their way through eight chapters that lead to the start of the film. The game uses atmospheric imagery from the film, directed by Guy Ritchie, bringing 1890s London to life, and players have their puzzle-solving skills challenged as well as their dexterity in a range of Flash mini-challenges.

The game is available for free but can only be played through Facebook. It has been created by AKQA and uses a natural language processing system, via which players can interrogate other characters in the game, and interactive crime scenes, where users can examine tiny details to find evidence.

Sue Kroll, president of Warner Bros. Pictures worldwide marketing, said: "Due to the iconic stature of Sherlock Holmes across the globe, we wanted to offer moviegoers the opportunity to enter Holmes's world. In addition to seeing the movie's trailers and other content, fans can actually interact as one of the main characters and test the same skills that Holmes and Watson need in the movie, using the most stunning new technology available."

The film is out on Boxing Day. It stars Robert Downey Jr as Sherlock Holmes and Jude Law as Dr Watson.