Since opening in London in May 2004, Alan Bennett’s first play in 12 years, of which this film is an adaptation, has sold out at almost every venue over hundreds of performances, winning countless awards – from Oliviers to Tonys – along the way.

Considering the subject matter, such an ecstatic response might seem rather odd, for in an age where theatre remains dominated by either Shakespeare, musicals that have been turned into films, like Chicago or Rent, or musical adaptations of films from The Lion King to Billy Elliot, such a small-scale piece of straight, philosophical drama went very much against the popular grain. Bennett may well be one of Britain’s best-loved playwrights, but rarely has even he met with such success.

Centered around a small class of history students preparing for their Oxbridge entrance examinations in a 1980s all-boys northern Grammar School, in the hands of a lesser writer this could have ended up an English Dead Poets Society. That schmaltzy American take on getting students to see the fascination at the heart of a school subject that many find boring, with Robin Williams at his most sick-making as the “inspirational” teacher, also remains typical of most films that have looked at the teacher/pupil relationship.

Bennett, however, has always been as interested in creating compelling characters as he has a message. Be it the carefully-crafted historical figures in his The Madness of King George, or is acutely observed studies in the everyday in his Talking Heads series, Bennett has long had a knack for creating entirely human characters with whom his audiences can instantly identify.

With the characters at the heart of the play, it is a definite blessing for the film adaptation that pretty much the entire cast of the stage version have been brought in to immortalise their interpretations of Bennett’s characters on celluloid. Left much longer, the “boys” – many of whom were in their 20s in any case – would have become far too old to convincingly play teenagers, and the masterly first production of a play that already seems to have secured its status as a modern classic would have been lost.

Another blessing is that stage director Nicholas Hynter – who also, in his capacity as director of the National Theatre, commissioned Bennett to write it – has returned to direct the film. Already confident in his actors’ abilities and knowledge of the material, he has been able to focus his attention on conjuring a realistic setting after the sparcity of the stage set. Having directed the superb film of Bennett’s The Madness of King George back in 1994, he is more than up to the task of bringing a play from stage to screen.

If you’ve been lucky enough to see the theatre version of the play you’ll know what to expect. For those who haven’t, this is an intelligent, amusing, heartwarming and original take on the much-explored coming-of-age themes familiar from countless plays, films and novels. But with Bennett’s writing, Hynter’s direction, and the wonderful work of a generous and extremely capable cast, it rises far above the vast majority of similar stories. As a slice of contemporary British theatrical culture, this is really one not to be missed.