IT is the eve of the First World War and a 14-year old naval cadet from a well-to-do family is expelled from a navy college believed guilty of stealing a five shilling postal order.

Ronnie Winslow, the Winslow Boy of the title, protests his innocence and his proud father insists his son's case is taken up by the most celebrated solicitor of the time. The subsequent two-year legal battle, loosely based on a real-life case, is heatedly discussed in the House of Commons and the national press as the affair becomes a cause celebre.

As Ronnie's elder carefree brother Dickie exclaims, what a lot of fuss over such a trifling matter.

Yes, the five-shilling postal order is only a dramatic device: it is the wider principle of justice and the characters' motives in pursuing it that is the point.

But when the crime is so piffling and its perpetrator largely relegated to a supporting role - mitigating against better understanding his character and establishing his innocence or otherwise - what one is largely left with is a study of the manners of the early 20th century upper class.

At the centre of director Christopher Morahan's fine adaptation of one of Terrence Rattigan's most celebrated plays is the accused boy's father Arthur Winslow (Edward Fox).

Fox gives a masterly performance as the archly patrician defender of the family name. His reliance on a walking stick and later a wheelchair betrays his autumnal years but with a resolute spirit and sharp brain and tongue he is feared by everyone apart from his spirited suffragette daughter Catherine (Lucy Akhurst).

When he learns of his son's expulsion, he summonses him to the living room and asks very slowly and very deliberately if he is guilty. "Don't lie to me Ronnie. You can't hide a lie from me." Such is his authority it's as if God is performing a lie detector test.

The snivelling, simpering Ronnie, played by the elfin Daniel Sharman, satisfies his father that he is innocent. His father, motivated perhaps by family pride and stubbornness, though he protests it's to ensure that "right be done", enlists the top QC of the day Sir Robert Morton (Simon Ward) to clear his son's name.

Sir Robert is not only a brilliant courtroom performer but a flamboyant MP with strident views at odds with those of the left-leaning Catherine Winslow. As Ronnie's elder sister, she suspects the "fish-like" and, to her mind, emotionally cold QC of only taking up the case for the publicity. Only much later does she discover she has badly misjudged him.

This Winslow Boy is a quality production, with a fine cast in command of its talents on an impressive set.

An examination of justice and the players involved in the legal game, it is laced with some dry one-liners, mostly uttered by the imperious Fox.

At a stamina-straining near three-hours, The Winslow Boy is nothing if not demanding - and perhaps a little over long - but represents the best of British theatre.

James Bowman

The Winslow Boy concludes its run at Guildford's Yvonne Arnaud Theatre tomorrow (Saturday) before a national tour.