As writer and star of raunchy romcom Trainwreck, American comedian Amy Schumer unleashes the drunken slut persona from her cable TV comedy sketch series Inside Amy Schumer, letting rip with a barrage of rude and raucous gags as her hard-partying New York singleton, a writer on a men’s magazine, tears through a series of riotous one-night stands.

Her boozy misadventures deliver some big laughs, but the film takes a surprisingly conventional and conservative turn when she begins dating Bill Hader’s good-natured Aaron, the successful sports doctor she has been commissioned to profile for her magazine. Amy’s discomfort at the very idea of a relationship initially keeps us chuckling, but the film loses its bite when it becomes clear that an old-fashioned happy-ever-after ending is in store.

Arguably, the film has already displayed a loss of nerve by taking pains to explain Amy’s promiscuity with flashbacks to her childhood as the daughter of a hard-drinking, womanising father (Colin Quinn). ‘Monogamy isn’t realistic’ is the lesson he dins into his two daughters, but it’s Amy and not her straight-laced sister Kim (played by Room Oscar-winner Brie Larson) who takes his maxim to heart.

Director Judd Apatow (Knocked Up, This Is Forty) is possibly to blame for steering Trainwreck into familiar romantic comedy territory, but Schumer’s taboo-busting gags still create quite a frisson.

Tilda Swinton, unrecognisable beneath an orange tan and flowing dirty-blonde wig, is hilarious as Schumer’s ruthless editor, and so is US basketball icon LeBron James, playing a droll, Downton Abbey-loving version of himself. Look out, too, for droll cameos from Daniel Radcliffe and Marisa Tomei in a black-and-white film within the film.

Certificate 15. Runtime 125 mins. Director Judd Apatow

Trainwreck is available on Blu-ray, DVD & Digital HD from Universal Pictures Home Entertainment and debuts today on Sky Movies Premiere.