ONE word, three syllables.

Mew. Lan. Coli (rhyming with e-coli). No wonder Paul Merton and his Comedy Store improv colleagues were momentarily nonplussed by an audience member's response to their request for ideas, the other week.

"We'd asked for an emotion, and this guy shouted out, 'Mew-lan-coli'," he says. "The audience laughed, and I got up and looked at him. And of course, he meant 'melancholy'. but he had never obviously said the word out loud before. I mean, this guy was in his thirties, you know ...How often do you use the word melancholy in speech? You don't, really." Merton is laughing now. "He had always thought this word was 'mew-lan-coli' - and only found out in front of 300 people that it wasn't."

Merton has demonstrated his remarkable improvisational skills time without number, on programmes such as TV's Have I Got News for You and Radio 4's Just a Minute. He adores live stage work above all else, though, which is why he and his Impro Chums - Richard Vranch, Lee Simpson, Mike McShane, and Merton's wife, Suki Webster - have hit the road again. They have three Scottish dates in mid-May.

He can't wait to be back on stage: he takes the view that "it's the most fun of all the mediums. There is no hiding place, no laughter track and no cutaways." The show, for the uninitiated, sees the comedians improvising sketches, at lighting speed, from suggestions called out by members of the audience. It can become surreal rather quickly. A Bulgarian lion-tamer trying to explain in fractured Spanish that the yoghurt in the fridge has gone off. That sort of thing.

The fact that Merton and his chums have known each other, and worked together, for a long time, has developed a distinct sense of teamwork in their live shows.

"If you're on each other's wavelength and you're friends offstage and you socialise together - you don't live in each other's pockets, by any means - three of us are regulars at the Comedy Store [in London] every week - and we tend to travel around together, so the onstage empathy is very important," he says.

"I've been in groups where two people are not having very good relations, they're always getting at each other, so you put them in a scene together and no matter what the scene is, they start playing an argument, they start shouting ... they start arguing about anything." Merton is laughing again. "So harmony amongst the people on stage is very useful.

"The empathy is very important - that's what you start building the imaginative scenes [with], layer upon layer, so they they build and end up in a very strange place, sometimes."

None of which, however, would be much good without an ability to listen. "You may have all sorts of funny ideas, but if I'm doing a scene with somebody and I haven't really listened to what they've said, I'll think, 'What's something funny that I can say now? Oh, I'll say this...' There's no connection going on.

"First of all, make sure you've heard what they're saying. There may be clues in what they're saying: they may be a blacksmith, for example.

"Whatever they say will inspire something in you. And if it doesn't - just look at them and say, 'What do you mean by that?'" And again that irresistible Merton laugh, so familiar from HIGNFY and Just a Minute, comes down the line.

At each interval, the audience can write suggestions on pieces of paper, which are given to the team. "We're trusting to the intelligence and the decency of our audience," he observes, "because this is an opportunity for people to write strange things under the cloak of anonymity. It's like our version of the internet, or trolling ...

"As you're picking them out of the bucket, occasionally there's one where you think, No, I don't think we're going to try to get comedy out of that situation'. It's usually something to do with a kidnapped child or something that's been in the news - we come to the theatre to get away from reality and horror."

Apologising for such a parochial question, I wonder if he has fond memories of gigs up here.

"Glasgow and Dublin audiences, as I've said in the past, have always been my favourite. Glasgow audiences are very bright and witty and not too combative. I mean, they do realise what we're doing is impossible, so as long as you realise that, then everything that happens after that is fine."

What does it feel like to have a large audience in the palm of your hand, helpless with laughter?

"It's exhilarating, absolutely exhilarating," Merton says. "My favourite moment is when the audience is absolutely helpless because someone's done some physical move and you've got a line in your head and you can't wait.

"But you will wait for the laughter to subside, because you've got the next line ... You say it. and it gets an even bigger laugh. That's great.

"The image that's coming to me now is like surfing a wave. It's fantastic fun, it really is just being at play."

It has long been Merton's dream to direct a cinema film and he says that he and Suki are working on a film script.

"We're on page 105 of our first draft screenplay. I can't give any titles away, or talk about what it's about at the moment, but the long, long held ambition is at least getting to a point we'd be able to ... It will be a low-budget British film, it won't be a big project or anything, in terms of finance."

He hopes that by the end of the improv tour (in June) "we'll be in a position to start having meetings with people about it."

I ask whether attracting funding might be a barrier. "The British film comedy is going through a bit of a boom period at the moment," he says, "mainly because The Inbetweeners film made a huge amount of money, the second one made a huge amount of money [according to reports, the first one took £45 million at the box office, with the sequel also doing well]."

"There are parallels with a previous time in British film history, in the 1970s, where ... " He breaks off. "Here's a good trivia question: in 1972, when The Godfather was a worldwide box-office hit, it was only Number Two in Britain because the Number One film that year was ..."

Something like Benny Hill?, I venture, searching my dusty memory vaults.

"On the Buses," comes the answer. "It made a fortune and it led to sequels, there were two Steptoe & Son films, there was Are You Being Served?, there was Rising Damp, everybody made a film. The same thing is happening now, because of The Inbetweeners." There have been other British TV comedy-based films recently, he observes; hopefully, he adds, there's a financial climate that is minded to look favourably on comedy projects.

Paul Merton, film director? It has a rather nice ring to it.

* Paul Merton Impro Chums: Aberdeen Music Hall, May 16; Inverness Eden Court, May 17; Glasgow Kings Theatre, May 18.