Surprise has been expressed over David Mamet wanting to make a movie of Terence Rattigan's decorous The Winslow Boy as if he were some roughneck seeking to be put up for the Athenaeum. But, like his mentor Harold Pinter, Mamet has long since cast off his early reputation as a chronicler of low-life and demonstrated his interest in, and ability to deal with, a wide range of themes and characters.

In fact, his decision to film The Winslow Boy is not unlike Pinter's to direct Noël Coward's Blithe Spirit at the National Theatre. It's a matter of respect for craft and recognition of affinities. One is reminded of Jorge Luis Borges's observation in his essay 'Kafka and his Precursors': 'The fact is that each writer creates his precursors. His work modifies our conception of the past, as it will modify the future.'

First performed in 1946, The Winslow Boy saw Rattigan, hitherto associated with light comedy, engaging with serious social themes by fictionalising the true-life Archer-Shee case. And like most of his plays (chief exceptions being his large-scale works about ambiguous gay heroes, Alexander the Great in Adventure Story and T.E. Lawrence in Ross ), it takes place on a single set, the Kensington drawing-room of Arthur Winslow, a prosperous 60-year-old banking executive, in the years immediately before World War One. Winslow, subtly impersonated by Nigel Hawthorne, is at the beginning a complacent patriarch, a wry humourist who speaks in terms of heavy irony. Punctilious in his use of language, he constantly interrogates others, but he lives in a world where people proceed by indirection, hardly ever saying precisely what they mean.

On the point of retirement, he has his life that seems near to perfection - his pretty, competent, conventional wife (Gemma Jones) organises the household, his elder son Dickie is at Oxford, his younger son Ronnie is a cadet at the Osborne Naval College, his daughter Caterine (Rebecca Pidgeon), an outspoken suffragette, is shortly to marry an officer in the Household Cavalry.

His only worry is that Dickie, the feckless charmer, won't get into the Civil Service, but Winslow will find him a job in the bank, and anyway, the beloved 14-year-old Ronnie will uphold the family name in the Navy.

Then Ronnie is falsely accused of stealing a 10-shilling postal order and dismissed from Osborne by the Admiralty authorities, and the stability of the Winslows is threatened when Arthur sets out to vindicate his son by taking on the Establishment. The case becomes a cause célèbre , and an expensive one. The press make Ronnie the centre of notoriety; Dickie has to leave Oxford; Catherine's stuffy fiancé breaks off the engagement because of the scandal and her disappearing dowry; Mrs Winslow finds it difficult to make ends meet. Catherine makes common cause with Arthur because she feels British society is inherently unjust.

But why is Arthur doing this - pride, family honour, stubbornness, a sense of justice, a need to be accepted? And in addition to ruining his own health, what right has Winslow to sacrifice his nearest and dearest in pursuit of this crusade?

There are elements of the near contemporaneous Dreyfus Affair in the Winslow story, and the case even has its Emile Zola in the form of the great politician and barrister, Sir Robert Morton MP (Jeremy Northam), who agrees to represent the Winslows. But Dreyfus was sent to Devil's Island and the case exposed the fissures of a nation; Ronnie Winslow just goes to another school.

There is another way this story could have been told - by returning to the original facts of the Archer-Shee case, in which the family was Catholic, the story began in 1908, the older brother a Tory MP and the sister a Conservative. The politics and larger social dimensions might thus have been brought out.

Mamet, however, realises that the combination of cosiness and claustrophobia is part of the play's meaning and appeal. The strengths and concomitant weaknesses reside in its form as an old-fashioned 'well-made play'. Only rarely does his film leave the Winslows' home, usually unnecessarily and never to visit the dramatic events in the law courts, which are laboriously reported in a succession of set speeches.

The Winslow Boy is a domestic drama that not only deals with the tensions and unspoken conflicts within a family, but offers that family as a metaphor for British society at large. It is a period piece both in being about a society on the brink of undergoing the cataclysm of World War One, and in being written when Britain, probably for the last time, might have been viewed as a homogeneous family, and one that had survived and been strengthened by the experience of the Second World War.

Most of the words are from the original text, but Mamet writes pastiche Rattigan dialogue that is as convincing as Alaric Jans's pastiche Elgar-Vaughan Williams score. He makes us look again at Rattigan's structure and at his language, and there's something else he brings out, which is the echoes of Wilde. Fresh from appearing as Sir Robert Chiltern in the film of An Ideal Husband , Jeremy Northam plays Morton as a Wildean dandy, handling the epigraphs with the style of a performer. This is clearly what Rattigan wanted - his stage directions for Morton's first appearance state: 'He looks rather a fop, and his supercilious expression bears out this view.' Now the model for Morton was anything but a supercilious fop. He was Sir Edward Carson, the great Ulster politician and advocate. As counsel for the Marquess of Queensberry, he destroyed Oscar Wilde, his old Trinity College, Dublin, contemporary, in the 1895 libel case that led to Wilde's downfall. Was the gay Rattigan making a point here?