No one has made such provocative theatrical fun of education, examinations and the relations between teachers and pupils as Alan Bennett in The History Boys. History itself plays a minor role, portrayed as a mysterious stranger who keeps looking in to ask hard questions.

Four seasons after its National Theatre premiere, after long tours at home and abroad, a West End season and Nicholas Hytner's film of the original, The History Boys makes a stronger, more emotional impact in Paul Miller's capable production than ever.

The improvement is primarily due to Desmond Barrit as the shambling Hector, the gayish schoolmaster who puts his heart into inspiring his charges and his hands into the crotches of late-teenage favourites, the entanglements beggaring-belief.

A bow-tied Barrit,with the drooping face of a long-since fallen angel and a voice whose intonations have a discreet hint of Frankie Howerd about them, puts on a hypnotic performance that captures Hector's comic eccentricities and the pathos of his introverted loneliness far better than Richard Griffiths managed in 2004.

Set in a 1980s northern grammar school, where David Mallinson's Headmaster determines to get his post A-level history specialists into Oxbridge, Bennett's play makes little sense realistically.

Organised in short, witty, eloquent scenes, with pupils spending absurdly long periods on general studies with Hector, The History Boys boasts a revue-like format. The cultural atmosphere seems far more 1950s than 1980s: the boys enact in French a hilarious brothel scene, mimic Celia Johnson's refined suffering in Brief Encounter, render a song from Pal Joey, make allusions to Formby and Gracie Fields.

They know Larkin and Auden, feel for Hardy's poetry. They generate intelligent fun. These young actors crackle and pop with talent.

Bennett, in his nostalgic formulation, applauds Hector as a teacher unconcerned about university education, who fires his pupil's imaginations. By contrast, the new history-tutor, Tim Delap's handsome but wooden Irwin, is wedded to materialism and recommends techniques designed to impress Oxbridge examiners. Gay desire unites these two teachers, both of them being closeted and emotionally frozen.

Andrew Hawley's cockily attractive bi-sexual Dakin, the History Boy who unbelievably attempts Irwin's seduction and inspires Daniel Fine's 1950s style sad-to-be gay Jewish class-mate Posner with unrequited passion, may command Bennett's admiration. Yet the beautiful closing scene of this flawed, poignant entertainment reveals an alternative hero.