You have to be prepared to go with the flow at a Phil Kay gig - and it can take you to the most unexpected places. At one memorable performance, he abandoned his routine in favour of leading a mock wedding service for the benefit of a hen party in the front row. "I was in the Queen's Hall in Edinburgh, which used to be a church," he recalls. "I got a bride and a groom up and ran through an entire wedding. I imagined that one family was rich and the other was poor. I noticed a giant bouquet backstage, so I ran off and got it. It looked like it had been planned, but it hadn't. It's easy if people are into it." They generally are.

On another occasion, "something went wrong with the sound. So I took 120 people and sneaked round to the cafe where the soundman was eating. We stole his food and told him the sound had gone wrong. You can't plan things like that. It was the most perfect, spontaneous, beautiful moment."

Spontaneity is Kay's trump-card. He can fire out pre-packed one-liners with the best of them - "What I love more than anything in the world is where you invent a brand-new Hoover and the international patents reap you millions."

But where he really scores is in forsaking his script entirely. "I never go on with the words worked out," he declares. "I know before I go on that I've got to do something about, say, brown sauce. But if you hold onto something that you must do, then people will see that. You have to let things go. You've got a tune, but you can still do a different song. I never get nervous because I've got nothing planned. I'm a great believer in running on and something happening. Once I ran on, fell over, and hit my thigh on the side of the stage. So I used that throughout the show; I kept going back to a `bruise update' on my thigh.

"Another night, I found this strange stepladder that I wore as a rucksack all evening," he continues. "Every night I'm open to these things. It's about a willingness to go with what appears important. Good shows are where you're Mister Mad and climbing the balcony. You have to be willing to leave your script. What you've got to believe is that random bunches of people are not always the same. Don't care what you're saying; just be into the people."

Phil Kay is at the Comedy Store, London SW1 (0171-344 4444) on Mon, as part of his Calder's Road to Edinburgh tour