An exotic new film accent has arrived, to be treasured alongside Dick Van Dyke’s Beverly Hills cockney in Mary Poppins, Michael Keaton’s lockjaw Mummersetshire in Much Ado About Nothing and Russell Crowe’s Geordie-Cornish-Glasgow in Robin Hood. Robert Downey Jr has had a crack at being Welsh (or has suffered a minor stroke) in Dolittle, a new version of Hugh Lofting’s novels about the eccentric Victorian gent who talks to the animals.

This is the family movie we didn’t know we needed. Because we really didn’t. The only justification of Dr Dolittle is to facilitate rude jokes in a Viz comic, but he has nonetheless made it to the screen with Eddie Murphy in 1998 and in the 1967 musical with stately Rex Harrison – a movie featured in Mark Harris’s brilliant book Scenes from a Revolution for being the hilariously out-of-touch best picture Oscar nominee alongside The Graduate, In the Heat of the Night, Chinatown and Bonnie and Clyde.

As played by Downey, Dr Dolittle has retreated into a hermit existence since the death of his wife, surrounded by GCI-mouthed animals, voiced by stars taking the easy paycheck; but he is summoned to the bedside of Queen Victoria (Jessie Buckley), who is gravely ill and surrounded by malign courtiers such as Lord Badgely (Jim Broadbent). Dolittle decrees that the cure comes from the fruit of the Eden tree on a remote island and so must voyage there with his animal pals in a Pirates-of the-Caribbean-y way and then voyage back, hoping against desperate hope that he is not too late.

Ranged against him is his dastardly brigand father-in-law, Rassouli (Antonio Banderas). There is also a spiteful and envious rival physician named Dr Blair Mudfly – Michael Sheen, playing someone called Blair for the second time in his career. What Sheen, born in Gwent, makes of Downey’s accent can only be imagined. It really is horribly inert, and every time Downey opens his mouth to say something unintelligible, the film dies a bit more. After just a few minutes, it is clear. He has done quite enough.

• Dolittle is released in the UK on 7 February.