Shaw’s Major Barbara is at root a pernicious play, the one that in 1905 gave a first warning of its author’s eventual mutation into the armchair revolutionary and anti-democrat who praised Stalin and Mussolini and excused Hitler. But it’s packed with wit, dramatic colour and articulate energy. It also has some terrific parts for actors, prime among them the armaments tycoon Andrew Undershaft, played in Nicholas Hytner’s fine revival by Simon Russell Beale.

Yet again this marvellous actor displays his range, transforming himself into a cool, watchful, quietly formidable character who effortlessly exudes authority and betrays his humble origins and inner strength mainly through a style of diction that combines bluntness with a growl in the throat. When Undershaft boasts of being “a manufacturer of mutilation and murder”, it’s as if he’s been gargling with cordite.

At the play’s core is a wager between him and his long-estranged daughter, the Salvationist Barbara, who asks him to her East End shelter, claiming that this will lead him to renounce his weaponry, while he issues a parallel challenge by inviting her to his cannon works. But it’s an uneven contest, for two main reasons. Hayley Atwell’s Barbara is warm and spirited but doesn’t have enough weight or intensity. And Shaw easily, if entertainingly, demolishes a Salvation Army that he believes should be snapping at an unjust social system instead of creating docile workers for the capitalists whose petty philanthropy finances it.

But the arch-capitalist is, of course, Undershaft himself. For much of the play he is callous going on demonic. Yet by the time the designer, Tom Pye, has moved us from a posh drawing room and a bleak shelter to the weapons factory, the tycoon has changed from prince of darkness to Shavian superman. Even Barbara accepts his argument, which is that the only ballot that matters has a bullet in it and that his weapons, sold evenhandedly to whoever will pay, will lead one day to what Shaw’s preface calls “a revolution of incalculable beneficence”. Tell that (say I) to the victims of Stalin, Mao and Pol Pot.

It’s pretty inconsistent stuff, with Undershaft, who began by rejecting the excuse that hideous weaponry makes war less likely, ending up challenging Barbara’s donnish fiancé to become his heir and “make war on war”. And though Hytner packs the stage with shiny, sinister, supposedly offputting shells for the last act, he can’t disguise that Shaw is gleefully recommending their indiscriminate use. And yet what wicked enjoyment there is en route to this unsettling close.

Clare Higgins was hilariously majestic as Barbara’s bullying mother and Paul Ready her mild-seeming, yet oddly tough, fiancé. John Heffernan, whom The Times followed through three months of rehearsals, was excellent as her wan, prim, ultra-conventional brother. And, of course, the great Beale: sophisticated yet somehow rough, given to long wary pauses – and more dangerous than that brilliant fool, Shaw, quite realised.

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