It’s always nice to come away from a movie pleasantly surprised. I was expecting more of the same from POTC: Dead Man’s Chest, laden down with endless in-jokes and gurning from Depp – and whilst both of those elements are certainly present they’re generally more charming than irritating, and rarely get in the way of the twisted fun that is this series’ real trademark.

And this time around, it’s a lot more twisted and only a fraction less fun. Three decades ago, Jack Sparrow made a deal with Davy Jones – he got to captain the Black Pearl for thirty years, the only catch being that at the end of that time he has to serve on the fabled Flying Dutchman for a hundred years. Unsurprisingly not so eager to fulfil his end of the bargain, Jack has decided to track down Jones’s heart instead, which has been buried in a box on an island for reasons far too baffling to go into.

Via circumstances that vary from the unlikely to the hopelessly contrived, Will Turner and his bride to be Elizabeth Swann, as well as pretty much every character from the first film, are soon drawn in to the quest. What follows is less a plot, more a meandering excuse for huge set pieces, comic interludes and the occasional splash of exposition – which would normally be a bad thing, but in a Pirates film seems to be par for the course. While it’s definitely too long and a touch too aimless, Verbinski at least never allows it to become dull.

The script’s greatest merit is that it has allowed its characters to grow in the space between films. Captain Sparrow, in particular, could easily have descended into parody – instead, Depp has turned him almost inside out. Stripped of his immortality and facing the horrible fate he’s set himself up for, Jack is cowardly, desperate and fairly despicable. The change may annoy die-hard fans, who’ll no doubt miss the first film’s emphasis on drunken fun, but it makes perfect narrative sense.

Meanwhile Bloom is less wooden than before, mainly because Will Turner’s relationship with his father gives his character the depth that it was missing. But Knightley, stuck with playing love interest to someone she spends most of the film’s running time apart from, becomes more superfluous with each passing scene.

As for the new arrivals, Nighy is decent enough as Davy Jones, managing a degree of nuance beneath a wall of CGI and make-up; however it’s Stellan Skarsgård as “Bootstrap” Bill Turner who gives the film’s only great performance, closely followed by Naomie Harris, who finds unnerving depths in her mcguffin role of all-knowing voodoo lady.

But what makes this sequel so enjoyable, (and so much better than the first), is the world that these characters drift through. It’s beautifully designed down to the smallest detail, and this time the effects work is good enough to do it full justice. In fact, the computer imagery is probably the best yet seen – particularly Davy Jones, his fish-friendly crew and his pet sea-monster the Kraken, which provides the year’s single greatest movie spectacle so far.

Gore Verbinski and his writing team have refined every aspect of their cinematic leviathan, and the fictional Caribbean of Pirates is deliriously gothic, feeling at times more like an opium dream than any Disney ride. Dead Man’s Chest may be far from flawless – half an hour of cuts and an ending that does more than set up part three would have helped no end – but it does provide a wonderful and very weird place to spend two and a half hours.