It’s incredible that Paul Merton was ever allowed on Just a Minute. “Five years before I went on the show, a producer told me that mine wasn’t the sort of voice they heard on Radio 4,” says the 58-year-old comedian, in what back in the day would have been seen as an unbroadcastably earthy London accent.

In 1988, just before he made his debut on the radio panel game, they still had doubts. Ted Taylor, the worried producer, rang Merton up. “He thought he was booking Sid Vicious, I think, because he explained to me that they don’t swear. Then wanted to know what I was going to be wearing just in case I turned up in swastika gear.”

Little did Taylor realise that, for Merton, this was the realisation of a childhood dream. As a boy in the early 1970s, while his peers were listening to Bowie and T-Rex, Merton would be taping Just a Minute, to learn how to emulate the virtuosity of Kenneth Williams, Derek Nimmo, Peter Jones and Clement Freud.

Today the Sid Vicious of panel shows has become part of the establishment. On 22 February, when Just a Minute enters its 74th series, he will overtake the late Kenneth Williams to become the second most featured panellist on the show. Williams appeared 346 times. Monday’s show will be Merton’s 347th.

Kenneth Williams (left) and Nicholas Parsons in 1981. Photograph: BBC

Freud, who died in 2009, retains top position with 544 episodes. Does Merton plan to overtake him? “Clement had a 20-year start, so it would be tricky.” He’d have to record 32 series to catch up: that’s more than three series a year for a decade. Merton puts his face in his hands.

He’s unlikely ever to catch up with the 92-year-old host, Nicholas Parsons, who has presented all 864 episodes since the show’s launch in 1967. Indeed, Merton suggests one of the reasons he has stayed on the show for 28 years is because Parsons is such a “generous, sweet man”.

It was Merton rather than Parsons, though, who revolutionised Just a Minute, perhaps even saving it from the chop. “When I started with Clement, Peter and Derek, the atmosphere was like a gentleman’s club, with someone sitting in the corner reading anecdotes about Donald Wolfit. If a woman walked into the room, they stood up – which caught me out completely.”

It was not a happy show. “Sometimes there would be recordings where the four regulars would gang up on Nicholas. On one show, they talked about his first wife being more attractive than his second. I think producers had a bit of a torrid time – they couldn’t get new people on because it was a closed shop.”

Williams’ death in 1988 raised the prospect of the show being axed. His performances – elongating words to thwart the charge of hesitation; throwing flamboyant mock-tantrums; his whole needy, waspish shtick – were so distinctive that Just a Minute seemed unthinkable without him. But then Parsons met Merton on a short-lived TV show called Scruples and encouraged him to apply. Soon Merton found himself on the same panel as his childhood heroes. His presence changed everything.

“There was a view that Paul Merton’s come in, he’s fresh and different, and if we gradually bring in new people, maybe the show has legs.” And so it proved: Julian Clary, Graham Norton, Jenny Eclair, Sue Perkins, Ross Noble, Shappi Khorsandi and Gyles Brandreth have all helped to give Just a Minute a new lease of life. “It’s just as competitive as it was,” says Merton, “but looser and more fun. I think.”

Just a Minute, in case you don’t know, works like this. The host gives one of four contestants a topic to talk about for 60 seconds and they have to do so without hesitation, repetition or deviation. If another contestant reckons the speaker has broken a rule, they push a buzzer and get a point for a correct interruption, and then take over the subject for the rest of the minute.

“It seems easy,” says Merton, “but it’s like golf. Just watch Rory McIlroy play and try to copy him.” Why are you so good at it? “Practice. And the gift of the gab. It’s my favourite job. I love it.” He once won 12 shows on the trot. “I had to stop winning because I was becoming Man United and realised everybody wanted Leicester City to have a chance.”

Who have been the worst contestants? “Esther Rantzen was one. There’s an understanding that you won’t object to repetition of words like ‘I’ or ‘and’, but she did. Big mistake. If you start being pedantic, others do it right back.”

But has Just a Minute, like many TV and radio panel games, stayed too much of a gentleman’s club? “I don’t think so, not latterly at least,” he says. “I agree with having quotas. Just a Minute works best when there are women. That said, I have been guilty of sexist attitudes. I remember being on the show with two women and I thought: ‘This will be relaxing.’ We recorded it at the Hay-on-Wye festival and I won’t say who they were, but it was anything but relaxing. They were so tough and funny and competitive.” After the interview, I check the show’s database: he must mean Maureen Lipman and Pam Ayres.

Merton decided to be a comedian when he was a small boy. But he didn’t know how to realise that ambition. “There was no comedy circuit in London. There were northern clubs, but I wasn’t northern. There was Butlin’s, but that wasn’t me. Or there was Footlights if you’d been to Cambridge, like Peter Cook or the Not the Nine O’Clock News crowd. I hadn’t. There was no way in.”

Paul Merton and fellow comic Janey Godley recording Just a Minute

So, after leaving school, he worked for seven years as a clerical officer at Tooting employment office. “I remember I was 19 and they were already advising me to consider my pension options.” Then he saw Alexei Sayle. “People go on about seeing the Sex Pistols live. He was my Sex Pistols.” Inspired, Merton quit the civil service and gave himself five years to make it. His break came at 1.30am one April morning in 1982 at the Comedy Store in Soho. “I was last on the bill, so if I was shit it didn’t matter.” He had been working on his policeman-on-acid routine for six weeks. “I had a plastic policeman’s helmet under one arm, and a tiny notebook on which – ingeniously – I’d copied the gags so I couldn’t forget them. And I was speaking in this blank copper’s voice about how I’d travelled to the planet Zanussi.” Did it go well? “Incredibly well. People were laughing at the set-ups before the punchlines.”

Did he think his comedy career would involve so many panel shows? “I’m only in two. They suit my natural laziness. I couldn’t have written 500 sketch shows, but I could improvise on 500 panel shows. There are so many on TV because they’re popular and cheap. That doesn’t mean they’re easy.”

In 2007, novelist Will Self argued that Have I Got News for You had lost its edge. “I don’t think he had a good time on the show,” says Merton. “He made a joke about fisting, which didn’t go down too well. Say something that doesn’t work and the audience think, ‘Oh, I’m not sure I like you.’”

Time for Merton to go: he and Suki Webster, his third wife, are off for a South African safari holiday. Are you enjoying life? “I love it. This is the existence I wanted when I was 10.” He has fame, a happy marriage, a creatively fulfilling life – and no mobile phone or social media profile. “I decided not to do Twitter or Facebook because it’s like taking the vilest heckler home in my pocket. Why would I want to do that?”

That said, there’s always someone who’s ready to rain on Merton’s parade. One day, he recalls, he turned up at Broadcasting House to record a show. “Are you here for Just a Minute?” asked the doorman. “That’s right.” “The queue’s over there, sir.”

• Just a Minute is on BBC Radio 4 on Monday at 6.30pm