You can hear it coming from the tone of his voice. He sits in his studio at Broadcasting House, asking the opening questions neutrally enough; but then if the answers are affected, pompous or disingenuous, the irritability flows out of him uncontrollably. These are the moments we tune in to the Today programme to hear.
No one in British broadcasting flays the pompous, self-satisfied bore, the careless assumption of superiority, the mindless, lazy argument, better than John Humphrys. That is why the Conservative Party, when in government, used to accuse Today of having Labour sympathies. That is why Labour, when it came to power, swung round with risible speed from lecturing the Tories about the value of media independence to whingeing about him themselves.
I suppose I should do here what so many of Humphrys' angrier interviewees over the years have failed to do and declare an interest. He and I have been friends and allies for more than 20 years, and have seen each other through some difficult patches. Humphrys is through all that now. He has become the face, and the voice, of the BBC in ways that none of the rest of us has quite managed. Even from deep inside the belly of the corporation, where many of us become unaccountably muted at important moments, you can hear his Jonah-like cry.
He is an unequivocal Jonah. He feels that everything is going to smash, that no one quite does what they promised or what they ought to be doing. Just when you thought the BBC had begun to get it together, to spend the right amounts of money on turning itself into the world's best, Humphrys is there to tell you that it's being dumbed down and looks like crap. In other words, he treats the BBC as though it, too, is a pompous self-satisfied bore sitting across the table from him in the Today studio.
Playing devil's advocate is the function he performs better than anyone else anywhere, and his book is an excellent and amusing read, occasionally moving and full of the small detail and careful observation. Reading it is like having him sitting beside you and talking to you. It springs, just as his fiercest and most irritable questions do, from the heart of the man himself, unadulterated by calculation or the instinct for self-preservation.
I agree about most of the things he says, because he and I have changed from being the Lucky Jims of the BBC to becoming its elderly, tetchy Kingsley Amis and Philip Larkin. All the same, I have my doubts about some of his complaints about its news programmes. There is a powerful problem: people don't watch news programmes in the numbers they used to. So what should be done to win audiences back, without patronising them or serving up a diet of undifferentiated, ignorant pap? As late as the mid-1980s people still watched the news faithfully and in large numbers, because they felt it was somehow their duty. That time has passed.
Those of us who labour away at the news coalface may not like this, but we have to live with it. There is no bringing back the days when people watched the news as a duty, any more than we could bring back the days when cinema audiences stood to attention while the national anthem was played. What we have to do is win the interest of the viewers. If this means creating the kind of colourful sets of which John Humphrys disapproves, too bad. If it means starting off with some lesser but attractive story and dropping the more important, worthier items down the running order, let's think about it.
But if it means leaving out things we know to be important because we think they will bore the audience, then that would be censorship as shameful as anything on Chinese or Serbian television. A Pole, back in the days of the Berlin Wall and the Soviet Union, once asked me: "Do you mean to say that in your country, where you can tell everyone the truth, there are really newspapers which refuse to do it because they are more interested in scandal?" Yet nowadays news programmes are shuffled around to make room for uninterrupted showings of old James Bond movies, and they have been replaced by the purveyors of information-lite bulletins who refuse to broadcast anything serious in case people might think it was boring.
Our duty is to make our reporting as interesting and accessible as we can. If we don't bother, if we put serious things aside in favour of the silly or comfortable or merely local, then we are failing in our responsibilities. There is a simple rule of thumb by which viewers can judge for themselves whether the news they are watching has been dumbed-down: how much information are we being given from the outside world, as opposed to the cute, the consumerised and the mental chewing-gum with a social angle? If the answer turns out to be consistently below a third, then I share the judgement of my fellow old codger, John Humphrys: "The forward march of entertainment values against news values has begun to encroach."
But unlike him I don't believe it has yet happened at the BBC. True, the Six o'Clock News at present carries a lot of consumerist and purely local British items. But big institutions such as the BBC have a general approach, an overall average standard, which always seems to reassert itself after a time. And thank God, anyway, for the Nine o'Clock News, 50 per cent of which is now made up of foreign reporting. No news programme in Europe, and no serious newspaper in this or any other country, contains such a high proportion of information from the outside world.
Still, we need Humphrys to keep banging away at the subject. The more that people are worried about the possibility of the BBC dumbing-down, the harder it will be for anyone to do it. Humphrys, as ever, remains his own man. You can't buy him and you can't frighten him, and neither Downing Street nor the BBC itself can shut him up. With his questioning, irritable, plain man's tone he has had a deeper influence than any other broadcaster on the way the nation regards the people who run its affairs. We owe him a great deal.
John Simpson is the BBC's world affairs editor