There’s a lot to be said for the old school.

Arranging an interview with Sir David Frost requires no haggling with PRs, press lackeys or intermediaries. You simply phone up Frost’s production company and are, in an instant, put through to that distinct, much mimicked voice — one that’s being awfully nice to you, while its owner rustles through his no doubt crammed diary. You don’t dare contemplate with whom you will soon be sharing page space — Stephen Fry remembers Frost breaking off a conversation to greet another guest: “Boutros Boutros, always a pleasure” — but there is nobody too small in Frost’s universe. Charm has always been part of the offensive. A little too offensive for the late Peter Cook, who claimed his biggest regret was having rescued Frost from a swimming pool.

As well as unparalleled media savvy, this particular commodity has served Frost supremely well over his 47 years in television. Far from the savage young satirist of That Was the Week That Was, he has evolved into a genial breaker of bread with the great and good. Where Humphrys and Paxo twist the thumbscrews, Frost eases his guests into a nice warm bath, tenderly administering enough verbal loofah to exfoliate the demons. “You can put just as testing a question in a relaxed way as you can in a hectoring way,” he explains. “The late [Labour leader] John Smith said to me, ‘You have a way of asking beguiling questions with potentially lethal consequences.’ Which I’m happy to have on my coffin.”

Today, Frost is quite mellow himself — and unseasonably ochre — having returned hotfoot from Christmas in the Caribbean. He still represents about the most genial and attentive interviewee you are ever likely to encounter, bursting into the lobby in a sharp navy suit, pumping your hand, then ushering you into his cosy study, complete with fireplace and plumped sofa. The desk is piled with papers — cluttered enough to give the impression of a busy man, not messy enough to suggest he’s been reading them.

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Three months short of his 70th birthday, Frost these days is broadcasting’s éminence grise. His main gig is his weekly show Frost over the World, on Al Jazeera, a station maligned in America, unfairly, as an Al-Qaeda mouthpiece. In its English-language version, it has been building itself as an alternatively focused rival to CNN. His show is received in 130m homes in 100 countries, he declares: “The thing is that we in the West are chauvinistic in our interests.” He cites an interview with President Lula of Brazil: “Probably the most powerful man in South America, rarely, if ever, seen on British television.”

Frost has done them all — premiers, prime ministers, princes, presidents, including every American leader since Kennedy. What is regarded as his Magnum Chinwag, though, is the exclusive series of interviews he conducted in 1977 with the disgraced Richard Nixon. Less than three years after the former president’s resignation over Watergate, Frost got from him what those on Capitol Hill had failed to elicit — a mea culpa. “A 99.9 per cent apology,” as Frost puts it. Certainly the furthest Tricky Dicky would ever go.

It was a hell of a scoop, not least because Nixon, with his agile legal mind, could run down the clock surer than the most artful contestant on Just a Minute, droning away until a question had no meaning. Funnily enough, my powwow today is not without its own Nixonian moment, as Frost kicks off proceedings with a tribute to the late Benazir Bhutto, with whom he had spoken just days before her assassination — eating into valuable allotted interview time, but done with such heart, it seems rude to interrupt. Frost, though, has been in the game long enough to give you what you want. Soon he is in full Nixon anecdotal mode.

He hunches forward, affecting Nixon’s gruff, heavy-jowled demeanour, channelling the moment when the former president described how he had bade farewell to the White House staff: “ ‘I hope I haven’t let you down.’ ” Their silence had been so deafening that, on recalling this moment to Frost, it had rolled into the famous confession.

“ ‘I hope I haven’t let you down,’ ” growls the impersonating Frost. “ ‘Well... I had.’ ” (“I let down my friends, I let down the country, I let down our system of government,” Nixon had continued.) “That was a euphoric moment.” With 45m viewers for the first US broadcast — it was transmitted in four 90-minute segments — and millions more worldwide, it remains the highest-rated political interview in TV history.

In 2006, Frost/Nixon, Peter Morgan’s play about these events, was a critical hit in the West End and on Broadway. Now, with the same stars — Frank Langella as Nixon, Michael Sheen as Frost — comes the screen version. The film has been nominated for numerous awards and looks a strong contender for the Oscars. “What [the director] Ron Howard’s done, it’s not spectacular,” Frost says. “He didn’t do anything like putting scenes in the middle of a football field, but he opened it out emotionally. He did a terrific job.”

For the subject of a biographical film to give an interview on its behalf is an unusual thing, because a) they’re usually deceased, or b) are most likely in litigation. The royal family hardly went out of their way to promote Morgan’s The Queen. The writer had pitched the play to Frost as “a sort of intellectual Rocky”, and Frost had been sufficiently soft-soaped by tales of theatrical impoverishment (it opened at the Donmar Warehouse) to grant his UK rights for free.

Yet not for nothing is Frost one of the smoothest operators in the business, said to be worth about £20m. This time, he followed the money. “I take the royalty,” he whispers. There’s also his book, Frost/Nixon, co-authored with Bob Zelnick, the Washington journalist who led Frost’s research team, and the original television interviews, or rather the Watergate portion, released on DVD.

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