The first season of the beeb's latest costume drama, The Tudors, kicks off with a brisk assassination scene, followed by a noticeably less brisk scene involving a shockingly young, slim and beautiful Henry VIII (Jonathan Rhys Meyrs) bonking some random wench. He then pulls up his silly puffy trousers and declares war of France.

This is the show's way of telling us that we're watching real, gritty history - and to prepare ourselves for the panoply of mud, blood and nipples that lies ahead. It is also trying way too hard.

There's an awful lot wrong with The Tudors, and I don't just mean the flagrant historical inaccuracy of it. It has immense and sprawling cast of attractive but identical young men and impressively bosomed but identical young women, and it dawdles through ten meandering, appallingly paced episodes like a dawdling, meandering thing. It clearly believes historical events are only rendered palatable by the quantity of sword fighting and swyving you manage to bung into them, and yet doesn't have sufficient courage to commit to that wholesale and, therefore, will insist on dwelling on something tedious just because "it really happened like that, man." Take, for example, poor old William Compton, saddled for sheer shock value with a homosexual subplot with Thomas Tallis (yes, that Thomas Tallis, the composer, and no I didn't think he was bisexual either) who dies inconveniently of the sweating sickness because he really did - leaving the entire plot thread dangling there pointlessly, while Thomas bashes a lute over his grave (Tudor rock star that he was) and goes off to have a relationship with the woman he historically married. Take, for that matter, the entire episode about the sweating sickness - a more tedious hour of television I can't currently recall, and sadly devoid of the Tudor nipple quotient you have by that stage come to expect from the show, yet nevertheless the sweating sickness comes, everybody worries about it and/or dies, and then it goes away again, simply because that's what happened to have happened. It's an unfortunate approach, neither going far enough in one direction or the other, and although they have managed to make something of a coherent narrative out of Henry's personal and political decisions, the supporting cast are constrained by both on-screen time and actual history to behaving like mercurial goofs.

Some of the casting choices are equally boggling/hilarious/not quite enough of either. Although it's genuinely interesting to see a portrayal of Henry VIII as something other than a fat bastard with a chicken leg in one hand and the severed heads of his wives in the other, Jonathan Rhys Meyers is just too, well, pouty. I suppose it doesn't help that they keep dressing him in black leather tights and thigh high Tudor boots, but what could actually be quite an interesting exploration of his character at a significant time in his life is utterly ruined by the fact he's totally emo. Similarly, Sam Neill's Cardinal Woolsey spends almost the entire thing wearing a look of pained bewilderment - it almost comes as relief, I think as much to Sam Neill as to the viewer, when he finally gets round to committing suicide.

But, despite all this and, to be honest, considerably more, there is also something terribly fun about The Tudors. And, despite some catastrophic decisions, it's very occasionally almost good. Once it stops posturing and showing you nipples, and the story really begins to focus on its strongest elements, it's genuinely absorbing stuff. The opening credits insist: "You think you know a story, but you only know how it ends. To get to the heart of the story, you have to go back to the beginning" and although this strikes me as yet more evidence of the 21st century obsession with origin stories, The Tudors really tries to run with it. We all know the story, or at least the outcome of it, but the Tudors manages to construct a psychologically plausible personal backdrop to the vast political events with which we are so familiar. It boils down to basically being about sex and power: Henry is spoiled, immature restless and simply unable to cope with the idea of not getting what he wants, however trivial (in this case the equally pouty Anne Boleyn) and, you know, that works for me. By the time the show reaches its final episode it has created something that feels genuinely rich and detailed; and has finally managed to find a comfortable balance in its melding of supposition, fictionalization and the narration of historical events. Let us hope this continues in the second series in which, I believe, a newly matured and hardened Henry has grown a mustache.

And will probably declare war on France.