The show was conceived by Moffat and Gatiss during train journeys to and from the Doctor Who production base in Cardiff, where they were both writers. They aspired to produce a modern-day version of Conan Doyle's stories in which Sherlock uses the technologies that are available to him today in order to help him solve crimes. Credited as co-creators, Moffat and Gatiss each write one episode per series, with the other written by Stephen Thompson. Hartswood Films produced the series for the BBC and co-produced it with WGBH Boston for its Masterpiece anthology series. The series is primarily filmed in Cardiff, although the production also uses a variety of other locations. North Gower Street in London was used for exterior shots of Holmes and Watson's 221B Baker Street residence.
Sherlock depicts "consulting detective" Holmes, assisting the Metropolitan Police Service, primarily Detective Inspector Greg Lestrade (Rupert Graves), in solving various crimes. Holmes is assisted by his flatmate, Dr John Watson, who has returned from military service in Afghanistan. Although the series depicts a variety of crimes and perpetrators, Holmes' conflict with his archnemesis Jim Moriarty (Andrew Scott) is a recurring feature. Pathologist Molly Hooper (Louise Brealey) assists Holmes in her laboratory. Other recurring roles include Una Stubbs as Mrs. Hudson, Holmes and Watson's landlady; and co-creator Mark Gatiss as Sherlock's brother, Mycroft Holmes.
After an unaired pilot in 2009, the first series of three 90-minute episodes was transmitted on BBC One and BBC HD in 2010, with a second series of three episodes first broadcast in 2012. Critical reception was extremely positive, with many reviews commending the quality of the writing, performances and direction. Sherlock has been nominated for numerous awards, including BAFTAs and Emmys, winning several across a variety of categories. The first two series have been released on DVD and Blu-ray, alongside tie-in editions of some of Conan Doyle's original books. Soundtrack albums from series one and two have also been released.