The Riddle of the Sphinx (Inside No. 9) was characterised by Pemberton as a thriller in the style of Anthony Shaffer's 1970 play "Sleuth", while Shearsmith identified the episode as particularly theatrical, in the style of "Sleuth" and Ira Levin's 1978 play "Deathtrap". BBC executives, according to Shearsmith, saw the episode as a cross between "Sleuth" and Willy Russell's 1980 play "Educating Rita" that read as if it had been authored by psychopaths. The executive producer Jon Plowman suggested that the first half of the episode plays out like a radio play. The word-play and tea-drinking in this part of the episode are, in the writers' opinion, very
James Shirley Shirley went to Ireland, under the patronage apparently of the Earl of Kildare. Three or four of his plays were produced by his friend John Ogilby in Dublin in the Werburgh Street Theatre, the first ever built in Ireland and at the time of Shirley's visit only one year old. During his Dublin stay, Shirley wrote "The Doubtful Heir", "The Royal Master", "The Constant Maid", and "St. Patrick for Ireland". In his absence from London, Queen Henrietta's Men sold off a dozen of his plays to the stationers, who published them in the late 1630s. Shirley, when he returned to