This is a very silly show. Very silly. It is a show that grows in silliness as the evening progresses. It is a show in need of a larger cast, but being an extraordinarily silly show, this doesn’t really matter.

Because everyone on stage hurls themselves into the silliness with exuberance. The story of Spamalot is well known: the lonely king, accompanied only by a trusty servant, searching for love and — equally unattainable — that chalice held by Our Lord at the Last Supper. He needs knights, he needs a shrubbery, he needs to face up to needling Frenchmen and has to be disarming in conflict (see it: you’ll understand what I mean!).

And now and then it comes to pass that the king (let’s call him Arthur) has to dismount his steed and sing a song or 17, often with a “soggy old blonde with her backside in a pond” (let’s call her The Lady of The Lake), or it might be with Sir Dennis Galahad or the Knight of Ni.

For this is the very silly amalgam of the Arthur/Camelot tale with the Monty Pythonic quest for the Holy Grail, wrought by Chief Amalgamator Eric Idle (who incidentally appears as God), together with a musical accompaniment and a few add-ons from other parts of the Python canon.

It is an entertainment full of turns. Todd Carty is well put-upon as Arthur’s servant Patsy (and gets to lead off the most famous song in the show — Always Look On The Bright Side of Life). Look out for Kit Orton — mostly as a funny Lancelot, but wonderfully droll as the French soldier who jeers at Arthur (“You empty headed animal food-trough wiper: I fart in your general direction. Your mother was a hamster and your father smelt of elderberries!”).

Marcus Brigstocke is King Arthur: he told me last week how pleasurable it was to throw off his usual performing persona and prance around and sing songs. Well, he is a somewhat lumbering presence and can’t really sing, but is endearing. The evening I went, he returned gloriously to his ranting roots and went for a member of the audience who was fiddling with a mobile.

Which leaves Bonnie Langford as The Lady of The Lake. I have to say that I had not really been aware of her since she was ten and Violet Elizabeth Bott on TV. But her musical and performing credentials over the years speak for themselves: she holds an audience superbly with a fine big-show voice.

Spamalot continues at the New Theatre until Saturday. Box office: 0844 871 3020 (www.atgtickets.co/oxford).