Sherlock Holmes will wield a blade rather than his razor-sharp intellect to fight crime in a new film by a British director specialising in violent movies, it was revealed today.

Guy Ritchie, who made his name with the crime caper Lock, Stock and Two Smoking Barrels — and his marriage to Madonna — insisted that his gangland-style film will be faithful to Sir Arthur Conan Doyle. He admitted, however, that there will be plenty of violence, although this plays only a minor part in the books.

He was speaking at a press conference to launch the shoot next week. Filming will take place in London over three months. St Paul's and surviving parts of Dickensian London will all feature.

The Hollywood actor Robert Downey Jr is not an obvious choice for the deerstalkered detective, although he is known — like Holmes — for dabbling with drugs. Even less obvious for Dr Watson's role is the British actor Jude Law, known more for heartthrob roles. Both were confirmed in the cast, but as Holmes once put it, it seems "a long shot, Watson; a very long shot".

There is no Moriarty, but a villain will be a composite of Holmes's adversaries. He will be played by Mark Strong, who has just starred in Ritchie's RocknRolla, a UK box-office hit despite mixed reviews.

Ritchie is to try to revive his career by giving Sherlock Holmes a gritty, contemporary interpretation.

Sherlock Holmes, to be released next year, has had an army of screenwriters. Their script is based on a comic book about Holmes by Lionel Wigram, a Briton who worked on the Harry Potter films.

Holmes has been absent from the screen since Rupert Everett revived him as an opium-smoking detective on television four years ago, a performance that for many could not compete with earlier classic depictions by Basil Rathbone and Jeremy Brett.

John Gibson, a leading Doyle expert, said: "Brett was so good [as Holmes] that he spoilt it for generations to come."

Hearing about the violence in the new film, he said: "Holmes didn't resort much to violence. Only very occasionally. He was the cerebral detective who solved [crime] by pure intellect."

Ritchie said: "We can have a different take. I like to think a better take."

He will be competing against a rival Sherlock film, a comic version starring Sacha Baron Cohen —- whose Borat was one of the cinematic hits of 2006.

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