With confident financing – by Korda, Del Giudice, and especially Rank – British feature technicians had emerged at the end of the war possessed of a bravura the equal of Hollywood. Alwyn shared in the blossoming, his name joined on the credits with Boulting, Launder and Gilliat, Neame, Roy Baker, Asquith, Pelissier, Lean, Frend, Negulesco, Mackendrick, Hamer, Dearden … and others, including Carol Reed.

Quite possibly it was the association with Reed that brought Alwyn his first contract with Launder and Gilliat. Frank Launder and Sidney Gilliat had made their name as the directors of Millions Like Us (1943), but they had worked with Reed as scriptwriters and knew him well. More recently, Alwyn had worked on Shaw's Soldier–Sailor, which Launder scripted. After the war they joined Independent Producers, a loose confederation under the Rank umbrella, and called themselves Individual Pictures. Their first production was The Rake's Progress, which they wrote jointly, Launder produced, Gilliat directed, and Alwyn composed.

Alwyn's most remembered contribution is his “Calypso”, written to scent the studio-bound coffee plantation scenes with an aroma of local atmosphere. Strictly speaking the piece is both calypso and rumba, commencing and ending on a languid calypso rhythm, with a lively rumba in the middle section to accompany a montage. Two record companies pressed it at the time of the film's release, and it has been popular since. But the film has more interesting discoveries than this pastiche.

The Rake's Progress narrates the unhappy life of Vivian Kenway (Rex Harrison), a spoilt playboy sent down from Oxford in 1931. Sacked by a South American coffee company, he becomes a successful racing driver and marries a half-Jewish German girl Rikki (Lilli Palmer) to help her evade Nazi persecution. He treats her so badly that she attempts suicide, and he kills his father through drunken driving. After a series of degrading jobs, he finds fulfilment in the Army and dies heroically on a reconnaissance mission. Critics saw him as a true portrait of a pre-war type of personality, and today one can enjoy the film for its sly humour and bittersweetness, even though it never quite reaches the heart of real human tragedy.

The titles start with an engraving from Hogarth's “A Rake's Progress” (1735) and continue with a series of sketches by Feliks Topolski illustrating scenes from our own rake's misspent life.