Why is he so annoying to people? In part, it's his pugnacity - the kind which you glimpse even in the titles of early plays of his, such as Knuckle and Slag. In part, it's the perceived gap between his private life (affluence, Hampstead home, succession of beautiful partners, children at private school, etc) and the more austere morality of his plays.
In part, it's that he likes to attack the press, and the press - the British institution least able to take criticism from outsiders - is quick to bite back, especially when its antagonist is from the left.
The man who co-wrote Pravda ought not to be so surprised and hurt that his two Sunday Telegraph pieces were presented as a Kingsley Amis- or Paul Johnson-like defection to the right. In fact, his thinking about British politics has changed very little. If he's drawn to Major, who he sees as a humane moderator of Thatcherite excess, it's as a tragic hero fit for a Hare play, a man who, whatever his talents, is doomed to lead a party that's run out of steam. And if he criticises the Labour leader for fiddling with his rear-view mirror when he should be looking boldly ahead, it's because he worries how well Blair knows what his priorities are, "and how bloodily he must stick to them", in order to get elected.
Hare is no less a socialist than he ever was. But this doesn't stop him being misunderstood, especially by the Labour Party. There are still recriminations over Absence of War, his play about the election fought and lost by Labour leader George Jones, based in part on the 1992 Kinnock campaign, to which Hare was given privileged access.
Kinnock supporters such as Gerald Kaufman and Roy Hattersley denounced the play as a travesty; Kinnock himself told Hare he thought it a success theatrically, but painful for him to sit through "because it shows me as an arsehole".
The play wasn't intended as an attack on Kinnock, and for Richard Eyre's television version several of the more blatant parallels (a reference to Jones as a windbag, for example) have been removed, so that the play can stand as a fictional study in power. That it couldn't two years ago was partly because the election was so fresh in everyone's mind, but partly also because Hare had himself blurred the line between fact and invention by publishing his background research for the play in a book called Asking Around.
He had been astute and steely in getting his material. Yet he was nave in not anticipating how this would upset people - Patricia Hewitt, Philip Gould and others were furious at what they saw as a betrayal of privacy.
Interviewers use the word icy about him, but it's hard to see why. With his bright blue eyes and Michael Holroyd-like charm, he looks, in person, younger than in photographs, dismayingly handsome in fact, and more good- humoured. There's a touch of hauteur, a confidence in his own talents - but that, too, is understandable now that he's regularly spoken of along with Pinter and Stoppard as one of the great post-war British playwrights. And beneath the affability, there's a short fuse and a thick skin.
Even as an allusion to his tone as a playwright, icy doesn't seem to fit. The early plays could be schematic and severe, the characters programmed to embody Marxist or feminist ideology rather than to be themselves, but rereading them now the dialogue seems funnier than it was given credit for. In recent plays, he has become more interested in paradox than dialectic - in how honourable intentions can produce disastrous results, and how all characters are contradictory and ambiguous. Moral judgements are still passed - Hare is the most parsonical of our playwrights - but the judges are themselves judged in turn. There's a good example of this in Skylight, the new play, a comparatively intimate work by Hare's standards, which dramatises the relationship between a successful Eighties businessman (played by Michael Gambon) and a woman teacher in the East End. Each in turn delivers an angry denunciation of the other. But in their great debate - is it better to love people, or love a person? - there's no easy moral victory for either side.
At 47, Hare has no less of a capacity for anger than he ever did. But he is happier in his personal life - marriage to the fashion designer Nicole Farhi has brought him more than dress sense - and middle age has made him more benign and understanding towards his characters. Once he waged war on corrupt British institutions (the law, the church, the monarchy); now some of those institutions are being run by his contemporaries, and he's more appreciative of the ordinary people in them - policemen, teachers, vicars, civil servants - struggling to hold things together. Once, his enemies were lies and secrecy; now he explores how hard it is to be truthful. Once he dissected the harm done by our cringing dependence on authority; now Hare has developed an interest in what it is to be good.
The heroine of Skylight grows up being pushed by nannies beside stormy English seas, a background not unlike Hare's own. He was born in Bexhill- on-Sea, in 1947, into a petit bourgeois, semi-detached, optimistic post- war world. His mother was Scottish (she went to Paisley Grammar School, just like one of Hare's detractors, Andrew Neil) and her commitment to education and self-improvement rubbed off on young David, who went to Lancing School, on a scholarship, at 11.
His father was rarely at home: Hare likes to describe him as a sailor, for though he rose to be a purser with P&O, he began as a rebel and jackaroo, running off from Ilford for a life of adventure on the high seas.
The remoteness and enigma of his father have had a huge effect on Hare, making him wary of surrogate father-figures and male mentors (his closest relationships have been with women), and also leaving him with unusually intense feelings towards his adopted institutional homes, Lancing and then Cambridge. He's sometimes described as having the air of a public schoolboy, but if so it's in the Thirties mode of Auden and Isherwood (his left-wing politics arise partly from a distaste for the nannying effects of a public school education), and he admits to being a class fake who concealed, or over-compensated for his lower-middle-class origins by adopting a posh accent and dandyish manners.
At Cambridge, he was taught by Raymond Williams, whose earnest socialism might at any other time have made him more appealing to Hare than he was. But this was the mid-Sixties, anti-Vietnam war protests were in swing, and the world looked more exciting beyond the college gates. At 21, Hare founded the Portable Theatre Company, touring, writing and directing alternative agitprop plays with Tony Bicat and (later) Howard Brenton.
These days he bridles at the word polemical: his characters may voice strong opinions, but he reserves the right to hold different ones and dislikes the pressure on writers to become the equivalent of Any Questions panellists. Back then there were barricades to man, and he and Brenton had less time for talk of the sanctity of art.
Richard Eyre, at Nottingham Playhouse, was one of those who recognised Hare's talent. So, by 1978, did the National Theatre, which put on Plenty, his first major success. Hare is now the most-produced dramatist in the National's history (Skylight is his 10th play to be staged there), an anti-establishment playwright who has found his natural home in state theatre. Early on, no one was sure how to direct Hare - there were stumbling comparisons with Arthur Miller, Tennessee Williams and Bertolt Brecht - and his own directing aspirations created difficulties: Peter Hall found him "naturally paranoid, nervous and edgy".
But the partnership with Eyre, director of Skylight, is well-established and trusting, and suggestions for occasional re-writing do not provoke Pinterish or Dennis Potterish spleen. Despite the success of films such as Licking Hitler and Wetherby, Hare feels less secure in the cinema, and, fearing theatre to be imperilled, is more committed to the stage than he has ever been.
Between his first marriage, to the television producer Margaret Matheson (with whom he had three children), and his second, to Nicole Farhi, his private life was not always easily separated from his work. He lived at various times with the actresses Kate Nelligan, Penny Downie and Blair Brown. Unusual among post-war British playwrights in having written strong and independent roles for women, this has not prevented the charge of condescension and even misogyny. A touching, troubadour-like protectiveness seems nearer the mark. When the New York Times critic Frank Rich gave an indifferent review of The Secret Rapture (condemning the play to an early Broadway demise), and in particular deprecated Brown's performance in it, Hare wrote a furious open letter in response.
Despite his brushes with the press, journalism attracts him, and Asking Around shows how much legwork he puts in researching his plays: where most writers stay behind their desks, Hare has been out there looking. Critics and columnists might be irked by what he sees, but when future historians come to study the state of Britain in the late 20th century, Hare will be the playwright they turn to first.