Harry Potter and the Deathly Hallows, Part 2 (12A)

And lo! it has come to pass, the final Harry Potter film closes an eight-part saga which began 10 years ago yet seems to have been around for even longer. By the time the dust settles it will have generated untold revenues, created employment for thousands and given pleasure to millions. You might say it has been a small industry in itself: the British film industry. It is already being greeted with a yahooing triumphalism more often reserved for royal weddings and successful Olympic bids. Please pardon me if I don't punch the air; a quiet sigh of relief is as much as I can manage.

Not that part two of Harry Potter and the Deathly Hallows is bad, you understand; it's much better than I expected, given the mediocrity of the series in general and the fizzle of part one in particular. Director David Yates, aware of the need to go out on a high, keeps a steady hand on the tiller and a crisp pace as he navigates a plot that would bamboozle anyone – anyone, that is, apart from the legions of people who've read JK Rowling's book. It has seemed to me a signal drawback of the Potter franchise that, without a deep knowledge of the books, even the most willing cinema-goer would be hard pushed to make the smallest sense of it. Believe me, I've tried.

Here, in part two, we reach the point that's been a long time coming: the big showdown between Harry and the dread Voldemort, a force so evil he seems to have literally cut off his nose to spite his face. But, before that, we are hurried along with Harry, Ron and Hermione on their quest to destroy the last Horcruxes, items within which Voldemort has hidden shards of his very soul. They can be located anywhere or in anything, under such deep cover that not even a News International phone hacker could unearth them. But that won't put off our wizardly trio, and despite almost drowning in a sea of goblets (yes, goblets) and flying without a licence on the back of an albino dragon, they grab their penultimate Horcrux. The last one, which turns out to be the most vital, leads them back to Hogwarts Castle and the final conflict between Harry Potter and his snake-faced nemesis.

Yates stages some eye-catching set-pieces, enhanced by a wonderful production design (take a bow, Stuart Craig) mingling Mervyn Peake, Lewis Carroll and the spindly phantasmagoria of Ronald Searle. The bank of Gringotts, with its long, vaulted, hall and rows of goblin tellers, sets the tone of eerie wonderment: you never feel quite at your ease in this high-low world. Later, a pursuit and scramble over a vast repository of books and furniture looks like one of Nigel Molesworth's more macabre imaginings. Gothic frights abound. Severus Snape has always had something of the night about him, though a last-reel surprise reveals him to be a more ambiguous figure than I could have guessed. Alan Rickman (issuing pauses between his words that You. Could. Drive. A. Bus. Through.) has indulged camp too far in this series, but here nothing in his mannerism becomes him like the leaving of it. His fateful encounter with Voldemort and his snake, witnessed from behind a frosted glass door, is perhaps the best scene in the whole film.

Rickman and Ralph Fiennes have at least been allowed to develop a character. Most of the other British stars on parade have been less fortunate.

On the first tier Helena Bonham Carter, Jason Isaacs, Maggie Smith and Michael Gambon (as the pivotal Dumbledore) get a respectable chunk of screentime, but the likes of David Thewlis, Gary Oldman, John Hurt, Julie Walters, Helen McCrory, Jim Broadbent and Warwick Davis are obliged to fight for scraps. A slimming down of the cast might have enabled screenwriter Steve Kloves to give a smaller number of characters their due, instead of these blink-and-you-miss-them cameos cluttering the screen.

The interplay of realism and fantasy is still a disfiguring problem. No doubt the books lay it out more coherently, but the logic of why certain things happen at certain times is pretty slapdash. Given the various wands and incantations at his disposal, it's not clear why Harry can do one thing but not another. Vanishings and impostures are licensed almost at will.

While one accepts that the violence has been shaped to the constraints of a "12A" certificate, surely the climactic battle between Voldemort and the Hogwarts faithful will prompt some to wonder why hardly any human being dies – not even from the masonry crashing off the battlements. By the end the place looks like Berlin in 1945, but the students look merely dazed and smudged.

As for the central trio who have carried the series from the start, they have been game and likeable, but unscintillating. I have yet to be convinced by Daniel Radcliffe's acting; Emma Watson and Rupert Grint have some promise about them, though it's only their stamina, not their range of nuance, that has been tested so far. The flash-forward right at the end of the film, when Harry, Ron and Hermione are middle-aged parents waving off their kids at King's Cross, actually affected me more than anything they did in the previous seven films. It's not just their passing on the baton – or the wand? – to another generation; it's a farewell to their own youth, which they have devoted (albeit for sensational reward) to the making of the Potter phenomenon. So they go, treading softly in the dreams of millions.