For those who want empty spectacle, come aboard. The third instalment of Disney's billion-dollar buccaneering franchise is just as simple-minded as its two predecessors but longer, louder, bigger, brasher.

Pirate ships spew from the deep, tumble over the edge of the world, and blow one another to bits in a storm-lashed maelstrom. Every 10 minutes or so - which is quite often at nearly three hours' running time - swords clash, guns roar, timbers shiver, and cannons and men skitter across decks like dice thrown by a giant.

It's sporadically exciting but the plot is both nonsensical and a rehash of the first two films. And the acting, including Johnny Depp's increasingly tiresome mockney showboating as Cap'n Jack Sparrow, is much less special than the effects.

None of which will stop producer Jerry Bruckheimer and director Gore Verbinski yo-ho-hoing all the way to the bank, I suspect. These men know not to mess with a winning formula, so all the main figures from the first two films are back, plus Chow Yun-Fat adding fiendish orientalism and Keith Richards having a laugh as Sparrow's dad.

This time around, at least, Orlando Bloom's wimpy Will is kept largely in the background, and Keira Knightley's Elizabeth has swapped her corset for something approaching a personality.

We learn early on that Bill Nighy's squid-faced Davy Jones, formerly a keeper of damned souls, has been pressed into service as the reaper of the seas by Tom Hollander's rapacious East India Company, and is massacring pirates.

Young lovers Will and Elizabeth join forces with their old foe Barbossa (Geoffrey Rush) to convene the pirates' Brethren Court to fight this threat. But Jack Sparrow, the gooseberry in the couple's endlessly unconsummated relationship, is one of the nine lords of the Brethren Court, so he must be rescued from the purgatory known as Davy Jones's Locker.

This is about as clear and convincing on screen as it reads in print. There is also a frankly risible attempt to explain Barbossa's resurrectionfollowing his death at the end of the first movie, and no attempt at all to explain why Elizabeth continues to risk life and slender, creamy limb among a bunch of scurvy pirates, rather than going home to open a hat shop, given Will' s obvious problems with commitment. Pick at one bit of this script, and it unravels.

Within its dumb limits, At World's End is exciting enough. It looks great - not just the spray and the fray, but the meticulously scrofulous figures cut by the cast.

Depp gets a few laughs but has the wind taken out of his sails by Rush - who embraces piratical gurning with pantomime enthusiasm - and by Keith Richards, who always did that act better anyway. Bloom is bland. Knightley is not called upon to stretch any acting muscles, but she does get to fight as well as look fetching in this one, as well as delivering a rousing, martial speech from the rigging.

Some progress from the first film, then. But not much.