It's the best screen adaptation I've seen of Vanity Fair, although admittedly I haven't watched the 1987 series yet. It takes liberties and waters down Thackeray's savagery into something blander and less interesting, but at the end of the day, it works. That's a rare thing. It stands up as a successful drama and it's entertaining. I'm coming to like the 1967 series more and more in hindsight, but it didn't really work and the 2004 film doesn't either.

Andrew Davies's dirty secret is that he's surreptitiously gutting and filletting Thackeray's novel, but doing so with such style and verve that it feels faithful even when it isn't. Vanity Fair is a challenging text. Instead of dutifully wrestling with that because it's a 19th century classic, Davies has had the courage to throw out everything he doesn't like and merrily write something he thinks is better. It's the kind of adaptation you get in movies more than TV. The results are a mixed bag, but I admire his brass neck. There's lots of reinvention here, but the one which drives everything else is the fact that we're meant to like Becky! This is, to put it mildly, a surprise. Davies has censored great chunks of Thackeray to achieve this, but achieve it he does. This Becky actually has human feelings, really does regard Amelia as her best friend and can radiate charm and sincerity even when we know she's lying. Her demolition job on George Osborne is done for the best of motives, to teach him a lesson and thus in the long run make him more faithful to Amelia. To her she's never anything but a good friend, which might startle anyone who remembers passages like this from Thackeray:

"And she left her bouquet and shawl by Amelia's side, and tripped off with George to dance. Women only know how to wound so. There is a poison on the tips of their little shafts, which stings a thousand times more than a man's blunter weapon. Our poor Emmy, who had never hated, never sneered all her life, was powerless in the hands of her remorseless little enemy."

Davies doesn't overdo it, though. The first couple of episodes in particular make this decision look like a stroke of genius. This Becky is far more entertaining and, oddly, truer in spirit than Susan Hampshire's ice queen in 1967, since it's easy to see why she's so popular. It's still clear that underneath all that charm she's a two-faced little manipulator, but that just makes her a more vivid protagonist. For a while we're even on her side! They've crafted a grand Dickensian caricature of 19th century society and are using it to throw horrible things in her direction. The early episodes in particular take delight in snobbery and grotesquery. Sir Pitt is both hilarious and vile, while his wife owns dogs that look like insect larvae. Vauxhall Gardens is practically a freak show. The more appalling Becky's trials, the funnier it all becomes.

Unfortunately Davies's approach unravels in the second half. It's always lively, strong and entertaining, but it's drifting ever further from Thackeray's original until eventually we're supposed to think it's a happy ending when Becky snares Jos. Might there be any chance of her murdering him? Don't be silly. Our plucky heroine wouldn't do such a horrid thing! I suspect she hasn't even been working as a prostitute, unlike the 1967 version, although I did approve of Davies's vigour in making her a heartless bitch towards her son. That might not sound so terrible, but: (a) it detracts from the Dobbin-Amelia ending, and (b) it forces the script to hurry over Becky's downfall at the hands of Steyn, Rawdon and the servants, whereas Thackeray's original was making us punch the air and sadistically delight in every bad thing that happens to her. Davies is throwing away the final episode, basically.

While I'm making negative comparisons, by the way, I also preferred 1967's Waterloo. That had been powerful. What we have here is okay, but nothing particularly memorable. What's more it also ends bathetically in a recreation of the battle, which is something we don't often see but unfortunately looks so daft that I can only think they were going for some kind of wrong-headed historical accuracy. See the soldiers... um, strolling along. Why aren't they running? They're like a sad bus queue. The director also tries to convey the chaos of battle through the usual lazy man's method of editing together random shots with no sense of geography or narrative. If they were going to go down this route, I must admit I'd have expected something more dynamic. Admittedly it's still perfectly watchable and I'd have probably been quite impressed if this had been the first Vanity Fair adaptation I'd seen, but as it is I thought this entire section of the story lacked power.

Those are big objections, but I don't know if you'd go so far as to call them problems. They're choices, or else missed opportunities. Then there are all the deft touches in the script, such as the clarity with which Davies brings out the theme of snobbery and social class. "I am a gentleman, though I am your son." I also appreciated the way Davies kept drawing parallels between Becky and Amelia, who are facing similar problems but tackling them in completely different ways. They lose their sons together, they're cut off by their husbands' families together and are even seen playing their pianos in consecutive scenes. Oh, and the production also manages to steer around the low-level racism with Sambo and Miss Swartz by making them characters rather than plot functions.

The episode also has my favourite cast of the three I've seen so far. There are a few weak or surprising choices, but it's never less than solid and one actor in particular is so brilliant as to be definitive. They're TV actors rather than movie stars, but that doesn't mean they're not worth watching. Here we have Gene Hunt from Ashes to Ashes, the original Kryten from Red Dwarf, Betty from Some Mothers Do 'Ave 'Em and another son of Edward Woodward. Sir Pitt Crawley is being played by David Bradley, whom I only knew as Argus Filch in the Harry Potter films and Cohen the Barbarian in The Colour of Magic, but it would seem that he's one of the biggest names in the cast and the winner of an Olivier Award from 1991. He's also brillliant, by the way. I love the fun he's having with the role. Another favourite of mine is Tim Woodward (son of Edward) as Mr John Osborne, which I'm coming to realise is one of the strongest roles of them all, and he's investing him with so much power that at one point I thought the character had gone mad.

Natasha Little and Frances Grey in the lead roles are both clearly the best versions I've seen so far, feeling true to how you'd imagine the characters and yet also being likeable. Grey's Amelia is far from intelligent and worryingly low in self-esteem, but she has her own kind of strength. Then you've got the grand old workhorses in the background. Eleanor Bron and Graham Crowden are there in little more than cameos, but the latter made me laugh just by being Crowden.

I adore the monsters. Miriam Margolyes is a bit too cuddly and nice for my tastes as Miss Crawley, but that's the casting director's fault rather than hers. She actually does quite well at being selfish and cynical. It's just that she's Miriam Margoyles. However I can't really imagine anyone doing better in their respective roles than either David Bradley or Tim Woodward, while I'm in awe of the choice they've made with Lord Steyn (this time correctly pronounced "Stain"). The man's terrifying! He's not the elegant aristocrat you might have been expecting, but a pit bull terrier on its hind legs. He looks like a prize fighter. I'm not convinced the actor wasn't coasting a little in his performance, but he's such an ugly sight that it doesn't really matter. Great Scott, that was brilliant. I love what they've done with Bute's manipulative wife, too.

Then you've got the male leads. Rawdon Crawley's the big disappointment. Much as Becky's being watered down, Rawdon's no longer a villain who's met his match but merely a decent sort of chap with an unfortunate moustache. However on the upside here we have: (a) my favourite Jos Sedley so far and (b) the best George Osborne you'll ever see. No one will ever do him better than Tom Ward. He's so sublime in the role that he becomes a gravitational singularity, warping the production around him through sheer force of personality. It's the Tom Ward show while he's on-screen, despite the fact that George Osborne is theoretically a stupid, slightly wishy-washy character whose plot function is mostly to be a triangulation point between Amelia and Becky. Not here. Ward's Osborne is a breathtaking son of a bitch with charm coming out of his ears but an ego so unstoppable that he doesn't really understand the concept of not doing whatever the hell he wants.

I wasn't sure about Philip Glenister, though. Oh, I've no issues with his performance. He's downright impressive, in fact, but I can't help preferring the "stout as an oak" Dobbin-ness of the adorable Bryan Marshall in 1967. However as with Margoyles, that's a question for the casting director rather than the actors themselves.

This certainly isn't a soft-soap aftershave commercial, though. The George-Amelia storyline gets downright brutal, which is a credit to both Grey and Ward. The sequence of Mr Sedley's bankruptcy is a tour de force, Becky's still a pretty nasty customer even if she's not as bad as Thackeray painted her and overall 19th century society seems like a genuinely dangerous place.

Murray Gold is being even more boisterous than usual on the soundtrack, incidentally, but I quite liked that. I also appreciated Becky and Amelia's sons taking their place in the story.

If nothing else, I'd say Andrew Davies deserves the credit for proving to Hollywood that Vanity Fair wasn't unfilmable after all and thus six years later causing the Reese Witherspoon film to happen. Overall, this adaptation is an achievement. Episode one is incredible, while episode two is bloody good as well. I don't really like the final episode, which had burnt its dramatic bridges by undermining Becky's evil and is thus a poor shadow of Thackeray's, but at any rate I can respect the integrity with which it's treating Dobbin and Amelia. At the end of the day, this is strong television. It's good costume drama and until part six it feels as if it's honouring the spirit of the original even if it's deviating from the letter.

Natasha Little has nice cleavage, by the way.