What a wicked pleasure it is to welcome the first anti-musical into the West End! Spamalot gives a welcome new twist to the term musical comedy. It pokes fun at musicals like Camelot that treat King Arthur and all the grail business as if these things happened the day before yesterday.

How sweet it also is to hear songs with silly lyrics that send up the style of instant moral uplift and dewyeyed yearning that characterise numbers from Rogers and Hammerstein to Andrew Lloyd Webber.

See pictures from the show here

Already a hyper-hit on Broadway, Spamalot is "lovingly ripped off" from the movie Monty Python And The Holy Grail. There is more, though, to the ripping than that. Even describing the show as spoof, send-up, pantomime, musical comedy, satire and surreal farce does not altogether convey its weird, anarchic flavour.

Python fanatics will surely love it. Others, like me, while frequently amused and relishing its bad taste may ultimately find it too much a disconnected collection of old jokes and sketches in Mike Nichols's immaculately drilled production.

Yet Eric Idle, Spamalot's book and lyric writer, has done more than brush up the best bits from the Holy Grail movie. His lyrics, together with the simple, catchy score he and John du Prez have written, gleefully mock the sentimentality and grave phoneyness of back-to-ancient-history musicals, let alone Arthurian romances and chivalric codes. They revel in 69 varieties of absurdity, parody and anachronistic nonsense, the sacred grail regarded as a super vitamin for the soul.

Tim Hatley's beautifully kitsch designs, with pantomimic forests, castles and contraptions - like the giant,wooden rabbit and God's very own, large foot - sets the jocular mood. Tim Curry's plummy voiced, characterless, uncomic King Arthur and his male servant Patsy, canter around on foot with the clicking of coconut shells as horses' hooves and find themselves in a funny old England. "I am not dead yet" sing defiant corpses in a plague village and the locals do not even recognise the monarch - "we're anarchosyndicalists".

Hannah Waddingham's Lady of the Lake and her thoroughly modern dancing Laker Girls looking pretty anarchic too. When the Lady gets to grip with Galahad - Sir Denis Galahad to be precise - their confession of love works a Brechtian treat by reminding us we're firmly in a world of musicals, not a version of mythical England.

"A sentimental song, that casts a magic spell. They will all hum along. We'll overact like hell," they vigorously sing. A similar trick is worked in what we are told is "a very expensive forest" or even in the show's unfunniest and pointless number, which insists you cannot succeed in show business without Jews.

God, voiced by delectable John Cleese, puts in an appearance, but only in the shape of a giant foot, and waxes irritable. "I'm God, you stupid tit," he majestically accuses as he drives the knights and Idle's rather idling book to start their grail search.

That familiar Holy Grail scene with the killer rabbit and French taunter - "I fart in your general direction" - makes me laugh again, as does the armless knight, the tap-dancers singing Always Look On The Bright Side Of Life and Tom Goodman-Hill's butch Sir Lancelot falling for Prince Herbert who zips into a gay chorus and identity. Spamalot makes me carp, but it puts frivolity and anarchy, malice and mockery back into musicals.