Frost and his wife, Lady Carina, have two homes. One is a Victorian pile in Chelsea where he holds an annual knees-up for the great and good, and where his wife holds sway over the decor and does her own interior design.

Asked to describe her style, Frost is momentarily lost for words. Eventually, he reveals that the decor is very green. There is a picture of Nelson Mandela in the lavatory, and a picture of Frost playing in a charity cricket match at the Oval with Michael Parkinson. Frost is wicket-keeper. He is still keen on sport and hopes to interview Ferguson over the summer. Frost might even have been a footballer himself — in his teens, he had a trial for Nottingham Forest.

So, what we know about the house is that it’s greenish and has a lavatory. Frost becomes far more animated when we turn to his other property, an 18th-century house in Hampshire. “I really enjoy wine,” he says, “and we have a proper vaulted cellar. It’s absolutely perfect. Unfortunately, the previous owners were teetotal. So they used the wine cellar for the central-heating units.”

Frost has lived in Chelsea for the past 25 years, ever since he married Carina. Yet his childhood was spent moving from house to house, as his father, a Methodist minister, moved around the country for his work.

Frost’s teenage years were spent at a manse in Gillingham, Kent, opposite the headquarters of a religious cult, the New and Latter House of Israel, known as the Jezreelites. “They were building a tower because they believed people were dragged up to heaven by their hair, and wanted to make the journey a little easier,” he explains. “They never cut their hair, and they never washed.”

After grammar school, the young Frost went to Cambridge, where he joined Footlights and began the career in satire that would lead him to present That Was the Week That Was and programmes such as The Frost Report. Having upset the political Establishment of the 1960s, he went on to become a political interviewer, famously interrogating Richard Nixon after his resignation. He has interviewed every British prime minister since Harold Wilson, and is now working on Gordon Brown. And, of course, there’s a quarter of a century of Through the Keyhole.

The nature of celebrity has changed little over the years, he says. In the 1960s, we had celebrity photographers. Now it’s chefs. But how have our homes changed? “There was a period in the 1990s when minimalist-modern was very much the rage,” he says. “In the new century, there is a return to some of the more traditional houses — the idyllic country-house properties.”

Eventually, Frost gently hints that we’ve run out of time. He must prepare for an interview for his show, Frost over the World, on Al Jazeera television. He was even wearing his make-up as we talked. Very nice, too.

Frost’s technique as an interviewer is to put his guests at ease, and it’s instructive to see him in action. As we leave his office, we shake hands and say goodbye. I pick up my belongings in the reception area, but he’s beside me again. We say goodbye and shake hands once more. He follows me to the lift, where we shake hands again.

So, if you are a celebrity who wishes to share your beautiful home with the viewing nation, you can be reassured. Frost and his colleagues might poke fun at your bric-a-brac, but they won’t half do it politely.

- Through the Keyhole is on BBC2 every weekday at 3.15pm

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