Paul Merton is apologetic; he feels partly responsible for the success of Boris Johnson.

Would the Tory MP have become London Mayor without gaining popularity on Have I Got News For You? The 56-year-old thinks not.

“The monster was definitely created in our studio,” he sighs.

A team captain since the show’s launch in 1990, the comedian has seen first-hand the transformative effect the show can have on the politicians who appear on it. “They like to be on the show but it’s a real high wire act; there’s kudos if they look like they have a sense of humour but if the joke’s on them they can start to look ridiculous.”

He still groans at the memory of Labour’s Neil Kinnock hosting the show. “He mistrusted every word he read from the autocue and spoke at such a slow pace you felt you’d rather kill yourself than hang on ’til the end of the sentence.” But Boris was different. “He’s a very shrewd man who realises that nobody fears the buffoon. He’d leave hair and make-up with his hair meticulously combed by the make-up artist, disappear round the back of the set then walk on with his hair all over the place. I think he has a mirror in his pocket to make sure it’s always attractively tousled.”

Merton in person is not dissimilar to the way he appears in public – dry and entertaining, one eyebrow permanently cocked at the peculiar world we live in.

A new series of Have I Got News For You has just begun – the 46th, although he can hardly believe it – and when we speak he’s poring over the day’s newspapers as homework.

Outside of filming he doesn’t really follow the news. But it’s a foolish man who appears on Have I Got News For You unprepared and he’s become adept at identifying the stories that might appear on that week’s show. He likes to keep his teammates a surprise, however.

“I don’t know who they are until I see their name on the dressing room door and sometimes I don’t even know then.”

Although his faraway expression might suggest otherwise, Merton’s mind is working furiously while the cameras roll. “Because I’m an improviser I listen,”

he explains. “The stand-ups who come on the show tend to talk because that’s what they’re used to doing on stage.”

One of the pleasures of the show is watching the interaction between Merton and fellow team captain Ian Hislop, and their teammates that week. “I’ve been told it’s very apparent when I’m sitting next to someone I don’t like,” he says with a laugh.

Merton’s poker-faced flights of fancy have become his trademark, along with a line in lurid shirts – “Where else would I get a chance to wear them outside television? If you wore that sort of thing on the streets people would throw bricks at you!”

But he’s surprisingly earnest when it comes to the business of comedy, a profession that saved him from working in the Job Centre in Tooting many moons ago. “February 29, 1980,”

he says fondly. “That’s when I left the civil service. I’d been waiting for a leap year date to come round so I wouldn’t forget the date. I’d wanted to get into performing comedy for ages and I thought I’d never do that as long as I had a nine-to-five job.”

London’s Comedy Store had opened a few years previously and Merton rhapsodises about the democratising effect it had on comedy.

“Before the Comedy Store there were only a few routes into comedy – Cambridge Footlights, holiday camps and working men’s clubs. None of those avenues were open to me. At the Comedy Store it didn’t matter who you were or where you’d come from, anyone could get up on stage.”

He has had a residency there every week since 1984, performing his beloved improv with the Comedy Store Players.

It keeps him “match fit” for HIGNFY and Radio 4’s Just A Minute, on which he is a long-standing panellist. He loves the spontaneity of improvisation and its ephemeral nature – no lines to learn, no jokes to agonise over, no bureaucracy. “If you can get over the idea you’re going on stage with nothing in your head and just have faith that something will come, it’s great fun.”

He is currently touring with his “Impro Chums” who include Suki Webster, his third wife and a fellow Comedy Store Player who is, he claims “12% funnier” than he is.

“Although I did have that figure quoted back to me once and was asked to justify how I’d arrived at it.”

The couple married in 2009, six years after Merton’s second wife Sarah Parkinson, who he had been with since his first marriage to Caroline Quentin, died of breast cancer. It was a terrible time for the star, who had nursed his wife through her final weeks, but he found comfort in comedy, heading to the Comedy Store not to perform but “just to be among people I knew”.

Even in childhood, Merton remembers being entranced by the power of laughter when he first saw a troupe of clowns at the circus.

He loved the idea of playing a part in it himself.

“The thought of creating something that generates these happy, joyful moments was really appealing.”

Although Merton’s forays into documentary-making have been wellreceived and he says he’d like to do more, it’s in comedy that he’s truly in his element. “When you’re laughing and those endorphins are released, nothing else matters. It’s a plane of pure joy.”

* Paul Merton’s Impro Chums are at Brighton Dome on Friday (October 18).

Call 01273 709709.

*Have I Got News For You continues on BBC One on Fridays