I’ve seen it twice, first at its premiere at the National in 2004, then in the West End. It’s been to Broadway, toured the planet and here it is back in the heart of our own theatreland. Why has Alan Bennett’s History Boys had an even longer and larger life than his The Madness of George III – or The Madness of King George as it was known in America, a country where numbers signify cinematic sequels, not sequential monarchs?

I’m not sure I’m right – shows can acquire an unstoppable momentum, accumulating success the way rocks accumulate snow – but I’d like to think that the play touches a contemporary nerve and confronts a contemporary anxiety. Isn’t the nation of Shakespeare and Auden, Hardy and the great Gracie Fields descending into a slick philistinism? Isn’t education becoming less a means of enriching minds than of greasing whatever mental wheels lead to success in the marketplace? Isn’t British culture itself moving from the dumps to the doldrums?

The play’s strength is, of course, that it raises these questions in a witty, funny way. There’s no more hilarious scene in London than the one in which Desmond Barrit’s Hector, the school’s large-minded, sexually flawed maverick, lets his class of Oxbridge hopefuls improvise an episode in a French brothel and then, when the headmaster appears to find a pupil without trousers, pretends that they’re performing a painful scene set in a First World War field hospital.

We’re to compare Hector with three other educators: David Mallinson as a headmaster obsessed with league tables; Elizabeth Bell as the practical schoolmarm whose job is to “teach five centuries of masculine ineptitude”; and Tim Delap’s Irwin, who is Bennett’s prime target in a play that’s set in the Thatcher era and attacks a utilitarianism that’s with us still.

Irwin’s aim is not to help the boys to unearth historical truths, but to impress bored examiners with startling fibs, such as suggesting that the Japanese and not the Americans were surprised by Pearl Harbor.

Bennett concentrates his dislike of opportunism on this character, giving him an afterlife as a show-off telly historian and a Blairite politician who plans to abolish trial by jury because “the loss of liberty is the price we pay for freedom”. It’s surprising he doesn’t have a stopover as a director of Waterstone’s, the book conglomerate Bennett has asked us to shun, only to be patronised by one of its executives as the thing he most dislikes being called: a national treasure.

Well, he’s still too original a figure to be glibly categorised. He has plenty that’s provocative to say about everything from British society to the matter that much preoccupies these sixth-formers: their sexual identities. And the play’s latest cast? Well, not everyone shines, but the boys are well up to scratch, as is Barrit himself, a Falstaffian figure with his vulnerable, crushed, even agonised moments. With him genially in the lead, it’s no wonder The History Boys still lives, still flourishes.

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