First Night: Spamalot, Palace Theatre, London

The Saturday matinee I saw of Spamalot in New York was one of the loneliest afternoons I have spent in a theatre. Everyone around me was jumping for joy. Even people in the long queue for returns were jumping for joy (though almost bound to fail). Me, I was well-nigh toxic with jet lag and feeling a weird emotional disconnect from the wildly enthusiastic Americans having the time of their lives around me.

That only goes to show that in watching (and indeed in making) a piece of theatre, context is everything. In London, 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 just given me the most deliriously silly and 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 basic material but to the phenomenal speed, wit, cheek and showbiz knowingness of the direction, which is 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 the creators of the piece have put the DNA of American musical theatre on stage, the double-helix (so to speak) like two counter-revolving glitzy staircases in some fabulously tacky yet oddly irresistible Las Vegas floor show. You might be thinking: Mmm, sounds a bit like Forbidden Broadway meets the Morte d'Arthur. Only a tiny bit, though. There's such a wonderful good nature to the spoofs of (and sometimes whizzingly swift allusions) to other musicals in this show that the faintly rancid, incestuous quality and competitiveness of Forbidden Broadway is sluiced right out of the hallucinatory pantomime-set picture (clever design by Tim Hatley).

The good nature, which lets the air into a show that would otherwise feel a bit relentless and 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/Hollywood musical. You haven't lived until you've seen a monk and a nun re-doing the Gene Kelly/Cyd Charisse he-throws-leggy-and-taller-woman-all-over-the-place dance (a nutty reference to the "Slaughter on Tenth Avenue" sequence in Singin' in the Rain ) or heard a song that is all about how at this stage of a musical you have to have this kind of song (the joke being that it is about nothing else than that) or - and here I felt that I might actually die of laughter - hearing the extraordinarily talented Hannah Waddington (who plays the Lady in the Lake) throw all words aside and do an insanely "vocalised" version of every shabby, show-off trick ever visited upon a song by a prodigious but terminally tasteless female ballad singer.

Ms Waddinton, who is as tall and beautiful as she is awe-inspiring, is part of 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 screwy, dangerously re-wired world we live in. Now I think it is a soothing and soaring vacation from it. In gratitude for a great evening, I send the creators this parody, written after the show and in its spirit (and with apologies to Lerner and Loewe): "In short, there's simply not/A more expedient spot/For trousering huge profits, boy/But here in Spamalot".