King of the castle: David Starkey returns to his pet subject, Henry VIII

Among the many alarming images in David Starkey's new television series on Henry VIII, there's one that makes the blood run cold. There's the Tower of London, of course – scene of centuries of torture, imprisonment and death. There's Catherine of Aragon (or rather, an actress playing Catherine of Aragon) waiting calmly to be superseded. There's a lingering shot of Anne Boleyn's frilly cuffs hovering over a pool of her blood.

And then there's the worst one of all. "Something harder, colder and more brutal than before," says a terrifying voice, and the camera then settles on a pair of cool eyes glittering behind glasses. David Starkey's voice. David Starkey's glasses.

The nation loves being lectured and hectored by the historian with a voice like a juggernaut just waiting to run you over. The nation loves being educated by a man once described as "the rudest in the country". It loves the beheadings and the hangings and the thumbscrews and the severed heads. It loves the cumulative sense that fools are not suffered gladly – that fools, indeed, are not suffered at all. The nation, however, doesn't have to interview him.

"They say, 'Are you for breakfast?'" says David Starkey, and I feel like nodding, but then I realise that he's talking about BBC Breakfast, which he's been on this morning, and BBC News 24, and BBC Scotland and Radio 5 Live and a pre-recording for PM. He's surprisingly polite for someone who's done a day's work in the time that I've stuffed down a croissant at Caffé Nero. He's so polite, in fact, that I feel even more nervous. "Shall we have coffee?" he says grandly, as the doorman nods us through a hefty door. "Shall we sit here? Is this all right for you?" Yes, I nod, and yes. I'll need coffee for the verbal cuts and thrusts and swipes that will follow. Does coffee go with mincemeat?

"Here", by the way, is The Ritz. Starkey, in Savile Row suit, silk tie and scarlet pocket handkerchief, looks as though he lives here. Actually, he lives in a pied-à-terre in Highbury, and a Georgian mansion in Kent. But I'm sure he could live at The Ritz if he wanted to. His books – largely on the Tudors – are bestsellers. His TV series have garnered fees never paid to a historian before. And he is hugely productive. Five media appearances before breakfast. Assuming that I am not breakfast.

It is, it's true, an unusually busy day for the monarchy, or at least for an expert on the monarchy. Gordon Brown has just announced a possible change to the rules of succession. "Isn't it wonderful," says Starkey, "in the middle of the worst financial crisis for a hundred years, that our prime minister concerns himself with altering the rules of succession? And that our MPs, who are just raising their noses from fiddling their expenses; the first thing they think of is the vital importance of equalising gender rights, which will have no impact for at least 60 or 70 years?"

Well, yes, but aren't notions of equality slightly ridiculous when it comes to the monarchy anyway? You could say that about 60 million of us suffer discrimination on that front. But Starkey, of course, is pro-monarchy. It would be like asking Rowan Williams to argue against God. Which, on second thoughts, he might happily do, but Starkey is no believer in the Anglican model of belief. He favours certainty, or at least the appearance of certainty. And he thinks that the British monarchy has been "remarkably successful at this process of slithering adaption, with, on the whole, very desirable consequences." It is, he adds, "wholly irrational", but it works. "Looking back," he says, "over the last few weeks, at Obama-olatry – I don't want to have to stand up every time my political leader comes into a room." No? You surprise me.

"All monarchies," he continues, "are catered to national requirements. They reflect the peculiar circumstances of the kingdom of which they are a product. If you're English, you sort of bathe in these lukewarm waters with almost no frontiers and no definitions, this vast ocean, rather than the nice little crisp fjord, and I think that in that sense the Scandinavian or Dutch monarchies have suddenly had a second lease of life. It would be very interesting to get Gordon Brown to write a one-line summary of what the British monarchy is for. For example, the only thing that's Belgian apart from Catholicism and chocolate and child-abuse is the monarchy."

This, I have to admit, is only a tiny, edited extract of the lecture on the monarchy to which I have just been treated. When I say "to which", I am obviously succumbing to the Starkey style, because he really does say "of which" in normal conversation, and he does speak in entire paragraphs, complete with sub-clauses, and he does throw in nice little details like the "crisp fjord" and the chocolate and the child-abuse, as if you were an undergraduate who might need waking up. What he doesn't do is pause. Which makes asking questions slightly difficult. Not that he has ever hesitated to butt in himself, but when someone else does, in radio debates, he'll say things like "if I might continue", as if the other person is being very, very rude.

But as minutes, nay millennia, tick away, I screw my courage to the sticking place, and do. So, he's a small-c conservative, who has said he is "not tortured with guilt because working-class people suffer". How far is his support for the monarchy part of his political world-view?

"Well," says Starkey, "my political persuasion, like most people's, shifted, and I was much more to the left when I was young. My father voted Labour and was, in local terms, a prominent trade unionist. My grandfather was solid working-class Tory, and my mother always voted Liberal. I suppose my politics remained essentially in the middle-of the-road Labour left until the end of the 1970s."

What happened next, he says, was the Callaghan years and "the awful sense of a nation falling apart". "It's how Labour governments end," he says matter-of-factly. "They blow the national finances."

And then he mentions Mervyn King's historic intervention last week, George V's negotiation of a national government in the Great Depression in 1931, the Queen's admiration for her grandfather, the South Sea Bubble, the Napoleonic wars, the boom of the 1920s, the accumulation and destruction of free-floating capital and the "ignorance and arrogance" of Gordon Brown in claiming that he could bring an end to boom and bust. And then he gets personal. "The slump," he says, "is what happened to my father."

The son of a charwoman, his father went to night school while working as an apprentice at the cotton machinery manufacturers Platt Brothers. "The day he completed his apprenticeship, he was sacked. He did not work again for just short of seven years. My father and my uncle twice walked to London in search of work. And it only ended with the discovery of this job up in Kendal, where I was born, in a little plant making industrial machines, where he then worked for the rest of his life. That's what the slump means to me. It's not an abstract notion."

Growing up in a family where his mother, a cleaner, "laboured endlessly balancing the accounts" taught him the value of money. "I say I've no interest in figures unless there's a pound sign in front of it," says the man who glides between his homes in a chauffeur-driven Daimler. "I was a pioneer in saying that if academics are worthy of their hire, they should be paid properly. And that's why, of course, when the various opportunities cropped up, I grasped them."

For most people, a childhood of near-poverty would be challenge enough, but that was only the start. Little David was born with two club feet and polio. His Quaker parents were "off-comers" (newcomers) in Kendal and that was "strongly felt". Oh, and he was gay. Except that it wasn't called that in those days. It wasn't, in fact, much cause for celebration. Still illegal and the source, as Starkey remembers, of "tremendously sordid scandal". He went to school, on his first day, in a pushchair because he was recovering from reconstructive surgery on his feet. He can still remember the "hideous subterranean light" in the hospital ward. But there was nothing wrong with his brain, or with his capacity for speech. Or, indeed, his self-confidence. Age five, he told his headmistress school dinners were inedible and that he would eat at home instead. Was he a rude child? "I don't think so," says Starkey, with a slightly camp sweep of the arm that verges on self-parody. "In many ways, I was probably rather polite. I was certainly schooled in good manners."

So where did "Dr Rude" come from? That, it turns out, was partly a construct. After a PhD (on the inner court of Henry VIII) that was "practically hailed as a masterpiece" and a "starry" career at Cambridge and "accelerated tenure" at the LSE, Starkey was, he says, feeling, for the first time, "a bit chippy". He'd had a 20-year protracted adolescence of sexual promiscuity in a London where "the gay scene was just discovering itself", which was a "wonderful liberation" but had "wasted a lot of time". And The Moral Maze, the Radio 4 programme that took a weekly look at an issue by cross-examining a range of "witnesses", proved the perfect vehicle for all this pent-up irritation. "I've always rather enjoyed fireworks and games," he says, "and I developed the device of the verbal cartoon. It was striking," he adds, with obvious relish, "how hopeless the lawyers were."

Starkey loved the whole thing: the gladiatorial combat, the "scent of the chase", and the heady rush of victory. "I'm afraid," he says, "I regard feelings rather like pavements. They're there to be trodden on." But he is swift to admit that he became a bit of a cartoon himself, and that much of the anger he brought to these encounters was the anger of the outsider. And now, he says, with something like a twinkle, all of that has been "entirely swallowed up in success and old age, and wealth". At a recent dinner, he says proudly, someone told him that he was "one of the many examples of the fact that success makes people quite nice".

Oh dear. We haven't talked about Henry. Henry VIII, source of obsessive interest for Starkey ever since that PhD, subject of his most recent book, Henry: Virtuous Prince, hailed as a masterpiece (now out in paperback), subject of his new TV series, and of a British Library exhibition he's curated, which aims to explore his inner life. Yes, I'm sure Henry is fascinating, too.

"You didn't bore me," says Starkey, when our time is up and the tape recorder is switched off. Well, Dr Rude, you'll be pleased to hear you didn't bore me either.

'Henry VIII: Mind of a Tyrant' starts on Channel 4 on Monday (9pm); 'Henry: Virtuous Prince' is published by Harper Perennial; 'Henry VIII: Man and Monarch' opens at the British Library on 23 April (www.bl.uk)