There’s a world in which Dirty Grandpa is a great, if lowbrow, comedy. Robert De Niro is perfectly suited to the eponymous role of smutty senior; he’s always been convincing at improvisational comedy (look at Mean Streets, or even Goodfellas) plus you buy him as someone who can still pull off one-armed push ups. Oh, Zac Efron is miscast as a preppy conservative, but the supporting cast – Adam Pally as a dog-milking degenerate, Aubrey Plaza as a hyper-sexed nymphette, Jason Mantzoukas as a jovial drug dealer – are aces, and director Dan Mazer is at least competent at overlaying the succession of dick jokes with the necessary sheen.

This is not that world. The prime culprit isn’t Mazer, though, but screenwriter John M. Phillips, making his Hollywood debut here. Amidst the typical clichés, he finds room for a cockeyed romantic subplot driven by the kind of insecure masculinity that regards being ‘pussywhipped’ as the worst thing imaginable (think The Hangover or Hot Tub Time Machine). There’s a laughably misguided attempt to tackle race, too – the film can’t seem to decide if De Niro’s character is retrogressively offensive or progressive, and neither quite work. The biggest problem, though? It’s just not funny.