Previously on Harry Potter...
An eleven-year old Harry prevailed over a trying situation where the ethereal form of Lord Voldemort came out of the back of Ian Hart's head.
He stabbed a giant snake with a special sword and killed a diary with one of the snake's fangs.
David Thewlis turned into a werewolf. Gary Oldman turned into a dog. Hermione turned back time just so some stupid horse thing with wings didn't get its head chopped off by the man from Middlemarch.
Robert Pattinson got killed by Timothy Spall.
Harry tried to find a mysterious prophecy that could have made the series a bit shorter. But the prophecy was destroyed by his clumsy friend.
Gary Oldman got killed by Helena Bonham Carter.
Some good guys came down the chimney to save the day - including the man from Middlemarch who finally agreed that Lord Voldemort might be a problem.
The last time we saw Harry (2009's Harry Potter And The Half-Blood Prince) he was getting kissy with his mate's sister, pissy with overly cryptic mentor Dumbledore and dissy with Aryan class rival Draco.
He also learned that the way for good to triumph over bad was to destroy the shards of Voldemort's soul hidden in a bunch of magical artefacts ('Horcruxes').
Michael Gambon got killed by Alan Rickman.
So now, Harry, Ron and Hermione have bunked off their final year at Hogwarts to track down the Horcruxes and rob Voldemort of his immortality, so that the world will never again have to watch something coming out of the back of Ian Hart's head.
Problem: no school, no structure. Previous Potters have swaddled the younger actors in a huddly comfort zone of each other. Stilted delivery was muffled by the bustle of Hogwarts crowd solidarity.
Here, they're caught out in the open - wrapped up warm in coathanger-fresh cardies but exposed to the unblinking camera eye. As the three leads blunder across field and forest, bickering, bargaining, deciphering clues and making little camps, there's nowhere to hide.
Watson, as ever, is the star - breezy and effortless and never over-rehearsed. But the acting cogs still whir and clunk behind Grint and Radcliffe's eyes, and Watson's dominance gives the three-header scenes a tiresome air of matriarchy – as if she's playing mum to a pair of clutzy teenagers.
But all three are emerging talents who've awkwardly grown into their craft as they've grown up in public. Their uneven performances are an inevitable side effect of the pressure exerted by the film's over-reverential treatment of Rowling's books.
The final story may well be colourful and complex, but, on this evidence, there's absolutely no artistic justification for a two-movie split.
It's muddled and meandering and over-stretched - like the book. It's padded with rambling asides - like the book...
Next: Conclusion [page-break]
Instead of filleting Rowling's original for what could have been a gripping and pacy finale roughly split into two major acts (the build-up to the final battle and the final battle itself), we're stuck with an overlong prequel to 2011's main event.
Two and a half hours of fumbling and foreplay which could have escalated into something elemental if it wasn't so joylessly chaperoned by the dual-movie structure.
To Yates' credit, he sidesteps the studio politics and gets on with the job - directing with artistry and invention.
He tempers the hormonal anguish and cryptic beardiness with stealthy nods to the story's adult themes: a terrifying, McCarthyist reinvention of the Ministry Of Magic; the empowered Death Eaters' fascistic fervour for non-magical ethnic cleansing - complete with Nazi-like red & black livery.
Theres a smart expansion of Alfonso Cuaron's Prisoner Of Azkaban horror-movie elements: jars and jolts, fake scares, scuttling bugs, sweat-lashed nightmares, torture, murder and - the horror! - accidental owl death...
This (yes...) darkness applies to both tone and appearance. An emphasis on gloomy night scenes numbs the FX magic and maybe explains the difficulties with 3D conversion.
Pick of the adults is Peter Mullan's extra-evil Death Eater Yaxley - all reptile eyes and baritone blood-lust, flailing and wailing and spraying his killing curses into the air like a devilish dervish.
Bonham Carter is wild and witchy, Fiennes steps out of the shadows and layers a little more ham onto Voldemort's bones, while Rickman - the best thing about the series by far - makes the most of his disappointingly brief screen-time, swooping into Voldemort's stronghold and calmly laying the ground for Harry's destruction - raven-black, oily, inscrutable.
But Yates' second-unit indulgences - screensaver sunsets, languid helicopter sweeps over travel-brochure panoramas - only emphasise the emptiness.
There simply isn't enough material to fill 150 minutes and the waffer-thin stretching exposes a misguided and grabby dual-movie strategy.
This is Potter on pause - the magic muted by bottom-line logic. And, instead of what could have been a glittering orchestral climax, we've been served an extended drum-roll.
The thunder before the lightning; the rumble on the tracks... Passable and occasionally potent, but a towering great tease that has no right to exist in isolation from the latter - better - part of the story.