Michael Coveney
WhatsOnStage
★★★★

Even when he was alive, you felt that Peter Barnes was the unjustly forgotten playwright of British theatre… this first play of his… hits you with the gale force of a shocking revelation. James McAvoy is giving a performance of almost overwhelming savagery and brio in the O'Toole role of Jack, the 14th Earl of Gurney. The show unravels not as a Marxian attack on posh people but a hubristic vaudeville of self-immolation and consumption… McAvoy's fizzing performance just about holds the whole show together, for director Jamie Lloyd, finishing his second Trafalgar Transformed season, goes totally for broke, as he should, backed by a snazzy and theatrical design by Soutra Gilmour and a great cast of enthusiastic vagabonds… Delightful helter-skelter stuff, too, from Kathryn Drysdale, Forbes Masson and Paul Leonard

Michael Billington
Guardian
★★★★

James McAvoy lends Jamie Lloyd's revival a no less astonishing physical bravura… there are times when Barnes's play betrays its age… But Barnes's play has as an intoxicating energy that allows characters to spring into song-and-dance at a moment's notice and still touches a few raw nerves… the play is held together by McAvoy's mesmerising performance… Lloyd's production keeps the action flowing smoothly on Soutra Gilmour's unitary set and, in a 14-strong cast, there are good performances… Given the liberal advances made over the past half-century, Barnes's play in some ways feels like an exuberant period piece. At other times, not least in its suggestion that Britain is still in the grip of a clannish establishment network, it remains all too chillingly relevant.

Henry Hitchings
Evening Standard
★★★

James McAvoy's immensely charismatic performance anchors this rare revival of Peter Barnes's subversive Sixties play. As Barnes's writing delivers pitch-black comedy that calls to mind the deranged magic of Monty Python (which it in fact pre-dates), the versatile McAvoy savours its wildness… McAvoy's journey through the play's different moods is a tour de force… Director Jamie Lloyd captures the hallucinatory spirit of the play and marshalls a strong cast… Yet while Barnes's assault on elitism hasn't lost its relevance, a lot of the satire is either heavy-handed or shrill. Lloyd doesn't hold back, giving the play's madness room to unfurl. But for all the vigour of his approach, its two and a half hours of anarchic energy are exhausting.

Dominic Cavendish
Daily Telegraph
★★★★

…Whatever you think of Peter Barnes's riotously funny-peculiar assault on the English upper class and their deranged tendencies… you have to chalk McAvoy's performance down as one of the year's must-sees… McAvoy has tremendous, infectious fun as this charismatic holy fool, a role taken by Peter O'Toole in the 1972 film version. Eyes glinting with mischief, smiling beatifically, he takes Barnes's luxuriantly freewheeling speeches at often breath-taking speed so that even when they jump the rails of sense, we're still hooked… The overall journey – and its satirical thrust – isn't hard to follow… Few directors have Lloyd's ability to transport us to the upper echelons of theatrical pleasure.

Dominic Maxwell
The Times
★★★★

Say what you like about The Ruling Class - and this absurdist, agitprop extravaganza won't leave anyone short of an opinion or two - but you can't say it's dull. James McAvoy's luminous turn… Jamie Lloyd's production finds the excess-all-areas tone to persuade us that this blackly comic tale of awful aristos is more than just a period piece… Yes, there are moments where you wonder if all this politically charged, pre-Python archness… is dazzling but dated. McAvoy, though, always hints at something deeper than Sixties satire… Subtle? Nope. It's witty, angry, ugly and alive, though. And McAvoy's bravura performance holds it all together… Don't expect an easy evening. Do expect a blast of theatrical energy that ensures this psychedelic oddity makes a strange kind of sense all over again.

The Ruling Class runs at Trafalgar Studios until 11 April