King Charles III (Birmingham Rep – Tour)

It was the toast of last year, first with its sold-out Almeida run and then in the West End. Bold and full of ideas, Mike Bartlett's 'future history' about a constitutional crisis after Charles accedes to the throne is an ambitious, adventurous and rather naughty expedition into quasi-classical territory.

Now the show has been recast for a national tour, with Robert Powell stepping into the regal shoes formerly occupied to great acclaim by Tim Pigott-Smith, while the Almeida's Rupert Goold shares directing credit on the tour with Whitney Mosery.

Powell's performance is wonderful. His Charles steers well clear of any kind of impersonation, instead offering a well thought-out and pensive character struggling with the dichotomy of finally being thrust into the limelight he's waited for all his life. His ambivalence about the personal sacrifice he has to make for his public duty is almost palpable, and Powell reveals a real man behind the mask of the monarch.

The company is strong across the board. Penelope Beaumont's Camilla is tender and supportive of her torn-apart husband, while Ben Righton and Jennifer Bryden make a highly credible pairing as William and Kate — again, not impersonations but believable incarnations of two people battling with themes bigger than them. Tim Treloar and Giles Taylor as a Welsh firebrand Prime Minister and his devious Tory opposite provide excellent support, sparking the crisis that drives the play's story.

Bartlett's project unfolds in cod-Shakespearean iambic pentameter, played out on a starkly formal set by Tom Scutt and interspersed with some appropriately stately music by Jocelyn Pook. The stiffness of the setting restricts much of the human aspects of the narrative, and there are plenty of jarring moments in which the classicism of the language Bartlett sets up is suddenly undermined with awkward modernisms such as "It freaked me out".

Authenticity proves a problem, too, with holes a mile wide in the basic constitutional assumptions the play makes. Motives are often wafer-thin, cataclysmic changes of mind happen almost on a whim and there's an utterly implausible subplot about Harry (the terrific Richard Glaves) wanting to becoming a commoner after a night out with a feisty republican girl called Jess (Lucy Phelps).

But Goold's ability to spot a winner is never in doubt. For all its faults, King Charles III earns enormous credit for its scale and ambition, and the performances in the touring version are universally superb. Full marks, then, to the Almeida for offering us out-of-towners the chance to catch up with what is already being dubbed a modern classic.

King Charles III runs at the Birmingham Rep until 19 September, after which it will embark on a UK tour. For more information, click here.