I went to see Terry Alderton at the Bloomsbury Theatre last night. Great fun and a full review will be in the Evening Standard on Tuesday. But one particular thing struck me. Alderton was ostensibly doing a new show, but various bits in it came from previous shows. Not just his general multi-personality style, but actual gags and routines.

A bit about finding his wife's vibrator collection in the wardrobe came from last year's show, as did, if my memory is still in working order, the bit wear he deflates himself. But most notably, when Alderton came on for the encore he was persuaded to do his trademark marauding monster, prowling and growling like a banshee with microphone stuck in his gob.

This is where a comedy gig is more like a rock gig than a theatrical play. In the same way you want a band to do their greatest hits, you want comedians to do new material but also the material that you first liked them for. The other night the same things happened with Omid Djalili. After a show that liberally peppered his work-in-development with quips from his last show, Tour of Duty, Djalili returned for an encore and bowed to audience pressure and did his "Godzilla getting into a hot bath" riff.

There is a constant tension between the tried and the untested. Getting the balance of mixing old and new is frequently difficult for a stand-up. Particularly when audience members do not all want the same thing. I remember when John Bishop first broke through a few years ago and had a run at the McEwan Hall in Edinburgh. He played to packed houses and did a pretty much all-new show. But on the night I saw him I overheard people afterwards complaining that he had not done routines they had seen him do on Live at the Apollo. Yet at the same time i'm sure if he had done those routines there would have been other people complaining that he did not do an all-new show.

I suspect Micky Flanagan risks the same response from some diehard supporters if he doesn't do his signature "Out out" routine on his current tour. Comedy is weird. The element of surprise is crucial to comedy yet just because the punters know the punchline does not mean that they do not want to hear the joke again. That's presumably why Lee Evans still does his Bohemian Rhapsody routine at the end of his show. It may not be the only thing his fans want to see but they would feel slightly cheated without it.

Comedians want to move on, but sometimes the audience won't let them. Ricky Gervais once told me that he did not want to do the David Brent dance ever again. Then a few years later, at the Concert for Diana in 2007, when he was having to fill time before Elton John came on, the audience demanded the dance. And, sure enough, Gervais did it.

I guess when something works it is hard to let it go. I should imagine the Rolling Stones will be churning out those antqiue favourites when they play Glastonbury this summer. On the other hand, one doesn't expect the Rolling Stones to come up with a new song to match Satisfaction or Paint It Black. One would hope that as long as a comedian is working there might be a fighting chance of a new classic routine emerging. Comedy audiences crave fresh jokes and comedians undoubtedly like coming up with fresh jokes. But who can blame them if they occasionally pull an old classic out of the bag.