“A CD lovingly ripped off from the new musical.” So says the sleeve. To which they might have added: “And many others besides.” Eric Idle and John Du Prez’s musicalisation of the movie Monty Python and the Holy Grail is one of those shows (a not very good one at that) where the laughter starts long before the old jokes land (if they land) and the cry to “bring out your dead!” might just as easily apply to the material with songs like “He is not dead yet” more inevitable than they are witty or inventive.

When I caught it in New York I guess I had hoped that the score might actually add something to the old formula. But with only a couple of notable exceptions, Idle and Du Prez treat their songs as merely an extension of one joke: that nothing, and I mean nothing, about Spamalot is original. It is, as it clearly states on the tin, a rip-off, a relentless mickey-take of all the musicals it not-so-lovingly lampoons. The best of it is the song that sets the tone for the whole show – “The song that goes like this” – which step by step takes us through the whole process of creating a generic big-sell number. In it Christopher Sieber’s breathy Sir Galahad (sounding for all the world like Colm Wilkinson in Les Mis) comes on strong to the pneumatic Sara Ramirez as the Lady of the Lake. The song builds “straight into the middle-eight – a bridge too far for me”. And inevitably there’s the key change: “Everyone can see we should have stayed in D!” It’s a duet to the death all right.

The other genuinely funny lyric is the big Act 2 set-piece “You won’t succeed on Broadway (if you don’t have any Jews)”, a kind of Fiddler on the Hoof where no expense is spared and no pun unturned to give Mel Brooks a run for his money. But, that apart, the best thing about this show is probably its title. In striving so earnestly to parody the formulaic it’s ended up being shamelessly formulaic itself. Spamalot is for the most part a lazy piece of recycling right down to the inclusion of “Always look on the bright side of life”. That’s the one Eric Idle and John Du Prez whistle all the way to the bank.