As a man who has made his living out of interviewing world leaders and A-list celebrities, Sir David Frost might have found it difficult to change sides.

But, as he tells Steve Pratt, he is thoroughly enjoying having questions fired at him on the one-man show circuit.

Sir David Frost points to his tie and tells me that he's only worn it for interviews with two people - one's me, the other's President George W Bush.

I'm impressed, but then it would be a very blas person who wasn't on meeting "the only person to have interviewed the last seven Presidents of the United States and the last six Prime Ministers of the United Kingdom", according to The Times.

Reading his CV offers the challenge of trying to think of some area of business - both show and company - in which he doesn't, or hasn't, had a finger. He's not afraid of listing his considerable achievements and dropping more than a few names into the conversation. No-one could accuse him of being shy and retiring, from his early days as host and co-creator of the BBC's satirical That Was The Week That Was, to his current post as interviewer of world leaders.

A visit to his Paradine company office off London's Kensington High Street re-affirms that Frost is a man who knows influential people. The walls are covered in framed photographs of him with such diverse famous faces as The Queen, Tony Blair, Nelson Mandela, Clint Eastwood, Ronald Reagan and Princess Diana. His book shelves are straining under the weight of heavyweight biographies, although I did spot a copy of The Low Starch Diet wedged between Thatcher: The Downing Street Years and Clinton: My Life.

As a man who makes a living interviewing world leaders and A-list celebrities, he knows how to make people feel at ease in order to get them to spill the beans more easily. Before I know it, he's supplied me with local angles - his eldest son is studying at Newcastle and he relates he was last in York interviewing the Archbishop of York when he claimed this was no longer a Christian country. And he's a good friend of former BBC Director General and Chancellor of York University Greg Dyke from the days Frost was joint founder of London Weekend Television and TV-am.

By now, pausing only to ask if I want to use a tape recorder for the interview, Frost is busy answering my first question before I've even asked it. This concerns the reason for my visit - An Audience With David Frost at York Grand Opera House this month. He's joined the celebrity one-man show circuit only recently but "they've been great fun to do and audiences have been terrific", he says. "I used to do a one-man show back in the Sixties and always kept in touch with comedy over the years with after-dinner and after-lunch speeches. It's nice to get back to all that."

The first half puts the accent on comedy, recalling shows with which he's been associated and clips of co-stars including John Cleese and the two Ronnies, Barker and Corbett. After the interval, the audience is invited to interrogate him. "We never run out of questions," he says. "It's great fun as the questions may be serious or anything. You just never know what people are going to ask."

Often, people want to know which interviewee he's most disliked. I'll let him tell you himself at his Audience, but it's nice to hear someone who answers honestly and doesn't take the easy option. He much admired Robert Kennedy for that very quality, displayed in the last interview he did - with Frost, of course - before his death. "I was really impressed by his directness and his self-deprecating quality, the attractive quality of refusing the easy way out. Phrases from that interview went into my vocabulary."

By now, the air is thick with smoke. The fug that hung over his office when I arrived has been supplemented by puffs from a large cigar he's lit up. From time to time, we're separated by a cloud of smoke resembling a mini-Hiroshima. His desk, or rather bank of desks, is piled high with folders, bursting with papers. Clearly the computer age hasn't caught up with him yet, although new technology is evident elsewhere in the office. "I'm afraid I'm a holdout," he says, explaining his lack of computer. "But I know everything on this desk here, although the ones at the back I'd have to move to find out ."

I wondered what he thought of the portrayal of himself in Not Only But Always, the C4 film about Peter Cook and Dudley Moore, but it appears this is only the tip of the iceberg. Peter Morgan, who wrote the TV drama about the famous Blair-Brown dinner, is now turning Frost's even-more-famous Nixon interviews ("the largest audience for a news interview in history" - New York Times) into a stage play.

"He's still working on the first draft but I'm looking forward to seeing it. We were talking about who he'd get to play me and he said the ideal person would be Kenneth Branagh," he says.

The real Frost will continue to present Breakfast With Frost on BBC1 for another six months at least. Although it's been announced the current affairs programme is ending, the deadline has been extended to take in the general election.

Not that he wants you to think he'll have nothing to do once the series ends, pointing out that he's signed up to do two years of what he calls "mega-interviews" on the BBC as well as other things.

With 21 years of Breakfast with Frost behind him, he's seen how politics and politicians have changed over the years. When he began interviewing, spin was what you did to wet laundry. "I think mainly it's got more sophisticated in a way," he says.

"There was blatant changing of the subject, which people did in the Sixties and Seventies. Politicians have realised they have to respond to the question to some extent rather than going off on their own tangent. That's too obvious now.

'There was a time when people made fatuously optimistic predictions about the results of the next election. What goes on is continuing to think of new ways to ask questions. So there's an ongoing game of chess in interviews."

By now, Frost is running late for a luncheon appointment and asks if we can finish the interview in the back of his chauffeur-driven Bentley on the way to the hotel. He's used to being on the move, as a regular cross-Atlantic commuter since doing the US versions of TW3. It was in America that he discovered the talk show, something British TV didn't have back then in the Sixties.

"I thought that I'd like to do a talk show, not just with showbusiness personalities but news makers," he recalls. In The Frost Programme, the host wasn't the only one doing the talking as audience participation was encouraged, although not to the extent of the protestors taking over the show as happened on one occasion.

Whoever he's interviewed, Frost has remained politically impartial, which he found "difficult but important". For that reason, he's never exercised his right to vote, not something he'd recommend for others. "By the time I did TW3 and was first eligible to vote in 1964, I'd already been involved in television dealing with politics as well. I thought it would be better if I didn't vote so no-one could say, 'He's a secret Conservative' or whatever."

The list of movers and shakers he's interviewed is a long and varied one. Some have been more confrontational, some more enjoyable than others. What he says about them all is that "it's a great privilege to sit down with these people because generally it's so interesting". There are new formats but the basic fascination of two people talking one-to-one will always be there, he feels.

He gets out of his car at the hotel and tells his chauffeur to take me wherever I want to go. As we pull away I notice another car, which has also just dropped off someone, bears the royal crest. Were they, perhaps, Sir David's luncheon guest? If they were, it was one name he didn't drop.

* An Audience With David Frost is at York Grand Opera House on January 31. Tickets 0870 606 3590.