Dormer follows Vinnie Jones, who made an appearance as Holmes's adversary Sebastian Moran, and John Hannah, who played the detective's ex-drug dealer. However, her character Adler is unlikely to make the trip to the drama's New York base, and is instead expected to appear in flashbacks set in Holmes's native London.
In the Elementary universe, Adler is the detective's former lover who was murdered by the as-yet-unseen villain Moriarty (another hotly anticipated piece of casting, yet to be announced). A three-episode story arc for the character will culminate in the two-hour season one finale (showing in the US on 16 May and shortly afterwards in the UK on Sky Living), as confirmed by the show's writers via America's TV Guide.
Elementary has faced criticism from some Sherlock Holmes fans for the decision to make the detective's partner Dr Watson female, handing Lucy Liu the role. But Dormer seems an excellent casting choice, with a proven track record in portraying entertainingly arch characters similar to Adler, the woman whose intellect comes close to matching that of Holmes.
As both Margaery Tyrell in fantasy drama Game of Thrones, and Anne Boleyn in historical romp The Tudors, she combines brains and feminine wiles to great effect in her pursuit of a king, while she is also known to British viewers as a formidable supernatural being in BBC3 drama The Fades.
The news of Dormer's casting comes on the same day that Lara Pulver, who plays a dominatrix version of Irene Adler in BBC1's Sherlock, told Radio Times she does not expect to reprise her role in the upcoming third series, which is currently in production.
The door is still open for Pulver ahead of an expected fourth series of Sherlock but, unlessElementary has some radical twists up its sleeve, Dormer's role is likely to be more shortlived.