The movieverse is littered with horrible boyfriends: Hugh Grant in Bridget Jones, Josh Harnett in The Virgin Suicides, Anthony Michael Hall in Edward Scissorhands. None of these gentlemen, however, can hold a candle to the emotional thuggery of Nate (Entourage's Adrian Grenier), Andy's petty, confidence-burgling, spousal-envying beau from The Devil Wears Prada.

There is, alas, something of the Nate about Gnomeo's behaviour in Sherlock Gnomes. The sequel to Gnomeo and Juliet – and likely the only film this year that can boast that it is "based on 'Romeo and Juliet' by William Shakespeare and 'Sherlock Holmes' by Sir Arthur Conan Doyle" – sees the headliners of the 2011 original relocate to a scruffy London garden.

Here, the elder gnomes, Lord Redbrick (Caine) and Lady Bluebury (Smith) announce they will be standing aside to make way for a younger generation of ornamental overlords, namely Gnomeo (McEvoy) and Juliet (Blunt). Juliet throws herself into her new duties, while (the suspiciously neck-bearded) Gnomeo goofs off and undermines her efforts.

Determined to stage a “grand romantic gesture”. Gnomeo breaks into a local florist and wrecks the place. It falls to dependable Juliet to rescue him. They return to the garden, bickering, only to realise that all of their family and friends – Benny (Lucas), Nanette the frog (Jensen), Fawn the deer (Osbourne) – have been kidnapped.

Might the dastardly Moriarty be behind this and a London-wide spate of disappearing garden accessories? Can Sherlock Gnomes (Depp) and Watson (Ejiofor) solve the case? And will Gnomeo and Juliet learn relationship lessons by observing the arrogant detective and his put-upon colleague?

There are not nearly enough jokes and – horror of horrors – they misuse "wherefore art thou?" But working from Ben Zazove's action-packed script, Kung Fu Panda director John Stevenson keeps the plot moving at a jaunty pace. There are wonderful illustrations of Sherlock's memory palace. Oscar-winners, comedians, rock-stars, and  R&B-stars converge into a lively ensemble.

And then there's the elephant in room. Johnny Depp was confirmed as the voice of Sherlock Gnomes in November 2015, before ex-wife Amber Heard's allegations of abuse, before his ex-employees filed a multi-claim lawsuit over unpaid wages and working conditions, and well before this week's claims that he attempted to punch a location manager on the set of LAbyrinth.

The timing of the release is unfortunate, especially as Depp’s comically self-absorbed Sherlock reminds you how much fun the actor can be.

Correction: an earlier version of this article incorrectly stated that Johnny Depp recorded his voice role in November 2015