Ealing Studios, in which he co-starred and received top-billing with Jack Hawkins, Sinden was contracted for seven years to the Rank Organisation at Pinewood Studios and subsequently had prominent roles in 23 movies during the 1950s and early 1960s, including Mogambo; Doctor in the House; Above Us the Waves; The Black Tent; Eyewitness; Doctor at Large; The Siege of Sidney Street and Twice Round the Daffodils. Sinden became associated with his character of "Benskin" in the Doctor film series as the duffel-coated medical student, regularly failing his finals and spending most of his time chasing pretty nurses, accompanied by his trade-mark "wolf-growl". Sinden was the recipient of several "audience-based" awards during this period, including "The actor who made most progress during 1954". In 1956, a profile was written on him which stated: Theatre Commercial theatre In 1949, he appeared in The Heiress at the Theatre Royal, Haymarket opposite Ralph Richardson and Peggy Ashcroft, directed by John Gielgud. In his Sky Arts documentary series Great West End Theatres, Sinden said that the play ran for 644 performances (19 months) and he was the only member of the cast not to have missed a performance: "As the play is the longest run in the [Haymarket] theatre's history, I therefore gave more consecutive performances in this theatre than any other actor since it was built in 1820." The management gave him an engraved silver ashtray as a present in recognition of the fact, which he showed in the episode. Theatre being his first "love", he was a noted farceur and won best actor awards for his appearances in the Ray Cooney farces Not Now, Darling (1967); Two into One (1984) and Out of Order (1990). In 1976, he was nominated for a Tony Award as Best Actor for his performance on Broadway as Arthur Wicksteed in Alan Bennett's comedy Habeas Corpus. His other notable leading performances in the commercial theatre included roles in productions such as There's a Girl in My Soup (1966); In Praise of Love (1973); An Enemy of the People (1975); Present Laughter (1981); The School for Scandal (1983); The Scarlet Pimpernel (1985); Major Barbara (1988); Diversions and Delights (one-man show as Oscar Wilde, 1989); She Stoops to Conquer (1993); That Good Night (1996) and Quartet (1999). Sinden was a leading figure in the campaign to found the Theatre Museum in London's Covent Garden in the 1980s. In 2007, Sinden