PRODUCTION NOTES / Improvisation is a risky business: Dan Patterson, producer of Whose Line Is It Anyway?, explains

MARK LEVESON (co-deviser) and myself spend an enormous amount of time preparing for the series. With improvisation it's all about odds, that a game is going to work and that a combination of people is going to work, so you try to ensure that everything else that could go wrong, doesn't. We tend to put as many games in as possible before one that we think might not work. If you can get three or four really good ones, the players and audience relax, otherwise it all becomes a terrible effort.

I don't know why it is, but it tends to be that the good shows have good audiences. There are some audiences that respond really well and laugh at anything, while others only laugh if you do jokes about sex. If I could find a way to guarantee a good audience I would market it, because it's the most important ingredient. Over the years, the fact that the people in the show are now stars, and that the people who come along tend to be fans, has made for a more responsive audience.

The problem is that we've done so many shows, it is now very unusual for someone to shout out something we've never had. We also get people specifically asking for the same thing. Whenever John Sessions was on, people were always asking for Restoration comedy because they'd seen him do it before. We haven't introduced a lot of people since the second series. At the beginning we had a weekly celeb, but we found the regulars were running faster. New people need four or five shows to come up to speed, and we can't afford that now; expectations are so high, you don't have the chance to fail.

We record roughly three times more than we need, recording 16 to 20 games per show. Sometimes it has still been pretty thin, with just enough material for the show and no more. Other times we can get another show's worth, which will go out in the end-of-series compilations.

One way the programme has changed is that we've made it more scene-based. The Americans are particularly good at building storylines; the English tend towards one-liners. I always include those games which have a consistently high strike-rate, like 'Film and Theatre Styles', 'Party Quirks' and 'Props', so I know I'll have a least 24 minutes of material. Each series, I'll come up with at least two new games with a high strike-rate; for this, the sixth, series, they're 'Stand, Sit, Lie Down' and 'Fixed Expressions'.

In the afternoon we'll play the games, but with different storylines and suggestions. It is genuinely improvised on the night. The only exception is the film. They do get to see two or three films, one of which will be the one they dub. We kill ourselves to make sure that they don't see the props or hear the situations. There's no point cheating, because it's never as good the second time.

While it's recording, I'm up in the gallery mentally editing the programme and working out whether we have got enough for the show or if I need to put another game in. Then there's six weeks of editing.

Out of all the shows I do, Whose Line is the one that takes the most work and the most stress, and it's the one that to the viewer looks like it's the most thrown together. It ages me.

'Whose Line Is It Anyway?', Fri C4