Whatever could have led diminutive megastar Elton John to bankroll a series of digimations headlining humble garden gnomes? The fragile tchotchkes debuted in Rocket Pictures’ 2011 venture Gnomeo & Juliet, which offered Ozzy Osbourne voicing an ornamental faun, a soundtrack of childproofed Elton hits, and near-unsurpassable novelty value.

This flatly functional sequel relocates the trinkets from Stratford to London, where G&J’s honeymoon is almost over – she’s spending too much time in the garden – and a spate of gnome thefts attracts the interest of Baker Street’s finest, voiced here by Mortdecai star Johnny Depp as the same old supercilious pseud.

What follows lacks Pixar’s ambition and rich subtexts – Ben Zazove’s simultaneously overworked and underpolished script proceeds along that quest narrative line worn thin by years of multiplex filler – but gets so far on a very British daftness that is not entirely without charm. There are flourishes in the animation, equivalents to the parakeets and palm trees that once graced the exec producer’s specs. Sherlock’s deductive processes are illustrated in lively, hand-drawn black-and-white sketches, and we get the mildly radical touch of an African-American Irene Adler, now a moll running a speakeasy for dolls – voiced, in a bid for exportability, by Mary J Blige.

The whole makes for painless, occasionally chuckle-worthy matinee viewing, but after two films, this still looks and feels like a franchise driven more by commercial calculation than creative inspiration. The formula sits a stratum or two too close to the surface: easily relatable little things for the little ones, plus bouncy discofied versions of I’m Still Standing for accompanying baby boomers. It remains to be seen whether future jaunts up this garden path can crowbar in anything as artful as Song for Guy or Someone Saved My Life Tonight.