Robert De Niro redoubles his efforts to trash his acting legacy with Dirty Grandpa, a crass comedy about a foul-mouthed, recently widowed military veteran who takes his uptight corporate lawyer grandson (Zac Efron) on a recklessly hedonistic road trip to Florida in a bid to loosen him up.

The gags are mostly witless, with Efron’s character coming in for repeated humiliation from a series of scrapes with frat boys, drug dealers and the police that leave him naked or befuddled or both.

Yet the stars are certainly game, as is Aubrey Plaza, who very nearly pulls off the film’s most ridiculously implausible role, a horny college student who has the hots for De Niro’s wrinkled old-timer.

Certificate 15. Runtime 98 mins. Director Dan Mazer

Dirty Granda is available on Blu-ray, DVD & EST from Lionsgate.