When the Lord Chamberlain banned Harley Granville Barker's 1907 "English tragedy," it was for reasons of sexual modesty. Barker's hero is Henry Trebell, an MP who is persuaded to work in a Conservative cabinet as the minister responsible for dissociating Church and State.

This bachelor's life-defining opportunity to affect the course and character of his country hits the buffers when his affair with a married woman results in pregnancy and potential scandal.

Yet, despite the Lord Chamberlain's motives, it's not the sexual intrigue in this play that grips. Rather it's the cold calculation with which the body politic responds to it.

There is always something fascinating about how the powerful operate behind closed doors. And in an age where formality and correct behaviour (whatever that is) were held as citadels of virtue, there's something enthralling about seeing that edifice crumble and the arrogant pomposity of men turn into panic.

Roger Michell's stylish, though overlong, production cleverly acknowledges the episodic structure of Barker's play. Towering sliding flats glide across the huge stage as inexorably as the passing of time. Within this cool setting, Olivia Williams puts in a fine performance as the emotionally overwrought Amy O'Connell, Trebell's lover. She is a character who is the opposite of what patriarchal Britain supposed women should be and, to that end, Williams transmits a physical disgust felt by O'Connell for an unwanted child.

But the laurel goes to Charles Edwards, among the most watchable actors of our time. No one is more convincing as English upper class.

If that sounds as if his range is narrower than it should be, don't be fooled. Instead of the insouciant charm deployed for previous roles, there's a cool, calculating intellectual core to his Trebell. It always fascinates, even if its loss feels less of a tragedy to us today than Barker would have liked.