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
Peter McKintosh Being Earnest, Hay Fever, Harvey, Dirty Rotten Scoundrels, Another Country, Viva Forever!, Death and the Maiden, Butley, Love Story, Prick Up Your Ears, Entertaining Mr Sloane, Donkeys’ Years, The Dumb Waiter, Fiddler on the Roof, A Woman of No Importance, Educating Rita, Shirley Valentine (West End); Guys and Dolls, Uncle Vanya, Antony and Cleopatra, The Scarlet Letter, Just So, Pal Joey, Another Country (Chichester Festival Theatre); Seven Brides for Seven Brothers, The Sound of Music, Crazy For You, Hello Dolly! (Regent’s Park Open Air Theatre); The Winslow Boy (Old Vic/Roundabout, NY); Noises Off (Old Vic/West End/UK tour); Our Country’s Good,