Eddie Izzard, Brighton Centre

Let’s be kind to Eddie Izzard. The guy has not long finished running 43 marathons in 51 days in aid of Sport Relief and the undeniably noble effort would take the puff out of anyone.

And just the day before this show, he had run a half marathon further along the South Coast from Eastbourne to his childhood home town of Bexhill-on-Sea to reopen their refurbished museum. So maybe the lacklustre performance I saw at the cavernous Brighton Centre was one-off and he’ll be back on form for the rest of his tour.

Izzard’s trademark comedy (“bollocks with more bollocks on top”, as he calls it) is surreal, extended riffs that have an entirely logical starting point and in which he then, layer upon layer, creates an alternative universe. At his best, Izzard is hilarious and provokes that most delicious of comedy experiences - at the same time both wanting and not wanting him to stop as his twisted logic takes him ever deeper into the realms of the ridiculous; it’s so funny it’s painful.

But there was little of that here and I don’t think it's a problem with the material. He has certainly chosen a meaty subject to deconstruct in Stripped; why he doesn’t believe in the existence of God, and why he thinks he can prove it. The first reason is that God doesn’t intervene in those lives he has supposedly created - “He doesn’t do after-sales service, I guess.”

Izzard then debunks Noah and the Ark, suggesting that the tigers and lions would have eaten everything in sight, with only a squirrel who took refuge in a biscuit tin - “What kind of biscuits?” - left to tell the tale. There are occasional flashes of genius, such as his take on the Bayeux Tapestry - “Weavers were the photojournalists of their day” - and by the time of Henry VIII they were paparazzi, “Just show us a bit of tit, Anne Boleyn.”

After the interval he talks about how civilisation, through the development of language, again proves there is no God - why didn’t he make animals talk, for instance? - and why Latin is a deservedly dead language (“all those endings”). The two routines - brilliantly inventive and delivered with great verbal dexterity - were more like old Eddie Izzard.

But much of the time it was as if the comic was just talking nonsense to himself and we weren’t in the room. He acknowledged he was drifting several times and at one point said: “Where does the word Brighton come from? Er... I can’t think of anything funny to say.” Rarely was the audience helpless with laughter; more often they smiled or laughed politely, and one interval Tweeter (messages were being shown on the three giant screens on stage) said it all: “You’re not in the moment yet, are you Eddie?”

It felt like laziness or even arrogance had crept into this seriously underpowered performance, a feeling not helped by Izzard’s arrival being heralded by loud music and a terrific light show, as if a rock star was about to come on stage. His timing was rock star, at least - 15 minutes late and no acknowledgement, let alone an apology - and it came after we had been treated to a trailer of his forthcoming film biography, Believe: The Eddie Izzard Story.

The trailer has a voiceover from Izzard, intoning deep thoughts - that we all need to have self-belief and that we should follow our dreams - in a serious voice. Very portentous. I sincerely hope I don't mean pretentious.

Eddie Izzard is at the Brighton Centre until 30 November, then touring UK and worldwide until 30 January 2010. Information

Believe: The Eddie Izzard Story is released next month