What a shock it is to realise that this great, ironic comedy by Bernard Shaw speaks to us with even more chilling urgency than it did at its 1905 premiere. For Major Barbara sketches a portrait of Britain in which Simon Russell Beale's devilishly persuasive manufacturer of war weapons, Andrew Undershaft, revels in the fact that his power is unassailable, that he stands high above the control of governments. Today when a prosecution alleging corruption over sale of arms to Saudi Arabia is abandoned on grounds of "national interest", or our "ethical" policy on sale of arms is reckoned impractical, Britain seems to have lost none of its eagerness to enrich itself by packing the world with fairly lethal weapons: Tom Pye's grimly imaginative design for the final scene in Undershaft's factory brims with munitions and war-heads.

Major Barbara, though, only refers to the eternal arms race to make scathing political points about something different. Shaw harks back thematically to his Mrs Warren's Profession, in which prostitution is accepted as an unexceptional trade for young women who have no other way of escaping poverty. The East End, self-made millionaire Undershaft, in matching style, uses the fortune he makes on war-weapons to give his well-paid workers happy and secure lives.

Shaw launches Major Barbara in sophisticated, drawing-room comedy style, with Clare Higgins's haughty Lady Britomart presiding over her twenty-something children, as if she were connected by language and breeding to Oscar Wilde's Lady Bracknell. The play then opens out in radical form and travels to the sombre, downmarket locale of a West Ham Salvation Army shelter, where the inmates speak a Cockney quite unknown in normal Edwardian drama. A thrilling war of ideas is launched. It involves Andrew's estranged daughter, Hayley Atwell's oddly subdued Major Barbara herself, a Salvation Army girl trying to do good, together with the man she loves, Adolphus Cusins whom Paul Ready does not make intellectually vivacious enough.

They are up against Undershaft, to whom imposing Russell Beale lends the remains of an East End accent and an impassioned certainty that ill- gotten gains from selling weaponry can be used for a good cause. Who though will rescue the poor and offer them a better deal? The financially insecure Salvationists at their West Ham warehouse shelter, which looks too vast in the Olivier's yawning spaces, feed the destitute with not much more than hope and charity as props. So when Undershaft offers the Salvation shelter thousands of pounds, earned from the sale of all those war-heads, the girl feels fatally compromised.

Nicholas Hytner's elegantly nuanced production conveys Shaw's jovial, comic cynicism, particularly in a perfect scene where Undershaft discovers his useless son is only fit for politics or journalism. Better still it captures the savage, Shavian irony of Cusins's duel of words with Undershaft. When Cusins accepts a post in Undershaft's warfare business he does so with vain hope of using profits to assist the underclass to come to power. Major Barbara remains a timeless play for today.