The silliness bar for this summer’s effects blockbusters has already been set high enough, one would have assumed, by Clash of the Titans, a shambolic unteaching aid for students of Greek myth everywhere. Still, if there was any name we could have trusted to vault over that bar, throwing his hat into a sort of silly-season Olympics, it was producer Jerry Bruckheimer.

With Prince of Persia: The Sands of Time, Bruckheimer barges into the computer game-crossover market, having already parlayed an adaptation of a rusting theme-park ride — Pirates of the Caribbean — into one of the most lucrative megaplex franchises ever mounted.

Now, it may be risking all critical credentials to admit such a thing, but I know about Prince of Persia. It was a charming game conceived by Jordan Mechner in 1989, fiendishly addictive and fluidly animated given the programming limitations of its era. In the last decade it was given a state-of-the-art revamp by Ubisoft and became a best-selling global brand, but the formula remained essentially the same: scale walls, jump chasms, swing from bars, puncture guards with your sword, and rescue the princess. It’s never been rocket science, but it’s really good fun.

Watching Mike Newell’s film replicate these aspects of the gameplay is instantly, and in a bad way, hilarious, because the cart has been put so clumsily before the horse — these acrobatics come from nowhere except the movie’s dutiful need to honour its wellspring.

Jake Gyllenhaal, who looks fittingly like a bearded computer nerd with a wrestler’s torso, stars as Dastan, a plucky young prince framed for assassinating his adoptive father, and seeking to prove his innocence by, well, leaping around minarets and dodging a variety of spiked weaponry. He’s eager and well-trained, adopts a highly unnecessary British accent, and is strangely coy about taking his shirt off, unless Bruckheimer decided in the editing room that homoerotic camp risked being a too-gay turn-off for the geek demographic.

Any effort to stem this particular tide is, I’m afraid, entirely in vain once you get a load of the screenplay. “Silly songs and scented smoke will do little for you now!” finger-wags someone, though I was too busy snorting with delight to note down who, exactly.

A lot of the kitschiest stuff falls to Titans alumna Gemma Arterton, whose aloof princess, dolled up in “exotic” fake tan and wafting around in someone’s idea of Harem Chic, sports the plummiest Rada vowels you could hope to hear in the pre-medieval desert. I can think of almost no one from whom the instruction “Collapse the passages to the chamber!” could issue more mirthfully, except maybe John Inman.

The story picks up, after a faintly catastrophic first hour, when the gimmick of a coveted dagger with the ability to reverse time is purloined from one of the recent games. Gyllenhaal’s Dastan gets the chance to undo all manner of hissy villainy from Ben Kingsley’s royal uncle, this essentially being Hamlet by way of The Lion King; while he’s at it, almost everyone’s mascara could do with a complete reapplication, too, but he’s a busy prince, and there’s an empire to rewind and save.

In a movie of wildly uneven technical virtues, the effects sometimes look unfinished, though a crumbling landslide towards the end is everything you could ask a crumbling landslide to be, I suppose. In the middle, we get an ostrich race, which is briefly amusing if a little undermotivated, unless welcome supporting ham Alfred Molina decided he simply had to add the role of a sixth-century ostrich-race promoter to his busy list of credits. Really, who could blame him?

Newell directs it all like a jolly uncle at Christmas time, hogging the kids’ new PlayStation, and doing so enthusiastically enough that no one has the heart to tell him he’s holding the controller upside down.