Arthurian legend purists, or even enthusiasts, would have had to swallow their pride and their preconceptions very hard last night to enjoy the opening episode of BBC One's 13-part retelling of the days of Camelot from the perspective of new-wizard-on-the-block Merlin, but for those of us who were holding our breath and hoping against hope that Auntie's latest Saturday night blockbuster series wouldn't be another turkey like Robin Hood, or, worse, another Bonekickers, that bated breath was released in a rousing cheer of appreciation. This time, they've really pulled it off.

Most renditions of the tale of Arthur, and his father Uther Pendragon (which I've long believed to be the single best name in the whole of mythology) would have it that Merlin had been bestriding the royal stage since long before Arthur was born, and that Camelot was Arthur's palace, and did not exist - at least, not as a castle - in the time of Uther. And, since we're on the subject, that far from hanging around Camelot as a maidservant, Guinevere was of high birth and did not meet Arthur until he was much older.

But that's the thing with myths. Pick them up, shake them about a bit and retell them as you will. If the characters are all there, you can get your dramatic licence stamped at the Post Office and do with them pretty much what you like. So if you're prepared to put those other Arthur and Merlin stories back on the shelf for a while, ignore the odd anachronistic appearance of a sandwich (which wasn't invented until the 17th century) and forgive the BBC's perpetual shallow casting (hello again Eve Myles! Welcome back yet again Anthony Head!) you will, like me, have found this series opener a most entertaining, satisfying and fulfilling romp.

The sets were sumptuous. If there's one thing the BBC can do well it's the middle ages. Gaius' study was, well, a study in traditional cracked leather tomes and interestlngly shaped flasks of coloured water. The beds were suitably wooden and covered in rags, the straw was well-strewn about the dungeon floors, and the stone walls looked extremely substantial. The script was pacy and well thought through and the dialogue struck a good balance between ancient and modern, and certainly avoided the dreadful pitfalls of barely recognisable street patois that Robin Hood fell into time and time again.

The magical special effects were very well realised and their use nicely restrained. With this kind of thing less is always more, and keeping the spell-count down is a sure way of keeping the anticipation up. Even the inevitable CGI, when it came in the shape of the dragon for whose call the episode was name, was nowhere near as bad as our own Mof had feared.

I may have shaken my metaphorical head at the fact that producers didn't look beyond BBC regular Eve Myles for the casting of bad witch turned bad Mary Collins, but even though it felt quite strange seeing Torchwood's Gwen Cooper in Uther's court, she made a pretty convincing villain. The new boys Colin Morgan and Bradley James commenced their roles with gusto and credibility too, and of course old stagers like John Hurt, Anthony Head and Richard Wilson can always be relied on to turn in good performances. Katie McGrath proved an inspired choice as Morgana, her representation of beauty with a hint of menace concealed not very far beneath the surface was pitch-perfect.

With all the hype that Merlin has enjoyed in recent weeks, I was seriously worried it would turn out to be nowhere near as good as it looked in the trailers. On this occasion I'm really pleased to be able to say I needn't have worried. It looks as though the BBC has finally got another Saturday night winner on its hands to stand alongside Doctor Who.