If you really want to laugh a lot, then buy a seat for 'Spamalot'. By Paul Taylor

The press night of the mega-hit musical version of Monty Python and the Holy Grail - with a book by one of the original Pythons, Eric Idle, and music by him and John du Prez - has given me the most loopily enjoyable evening in a theatre since Dame Edna was last in town. Yes, it leaves you that high and weak with laughter, thanks not just to the Python provenance of the material but to the phenomenal speed, wit, cheek and showbiz knowingness of the direction, by the great veteran, Mike Nichols.

So what kind of musical is Spamalot? Well, it's a hysterical collision between the barking nonsense and bite of Python and the whole crazy shebang of US showbiz. It sounds barmy, but it's as though its creators have put the DNA of American musical theatre on stage.

The good nature, which lets the air into a show that would otherwise feel a bit one-note, comes from two main aspects. First, there's the endearingly bonkers notion of making the characters in a medieval Grail legend the conscious creatures of an aspiring Broadway musical. You haven't lived until you've seen a monk and a nun redoing the Gene Kelly/Cyd Charisse dance from Singin' in the Rain. Or heard a song about how at this stage of a musical you have to have this kind of song. Or - and here I felt I might actually die of laughter - heard the extraordinarily talented Hannah Waddingham (the Lady in the Lake) do an insanely "vocalised" version of every shabby, show-off trick that has ever been visited upon a song by a terminally tasteless female ballad singer.

Waddingham, who is as tall and beautiful as she is awe-inspiring, is part of the second reason why the show is good-natured. She and the adorably poached-eyed and sleepily subversive Tim Curry, who plays Arthur, have the rare trick of being side-splitting and touching at the same time.

When I saw it in New York, I thought the show was too sealed off from the dangerously rewired world we live in. Now I think it is a soaring vacation from it. In gratitude for my evening, I send the show's creators this parody: "In short, there's simply not/ A more expedient spot/ For trousering huge profits, boy/ Than here in Spamalot".

Monty Python's Spamalot is at the Palace Theatre, London W1, until 31 March 2007