Mike Bartlett's brilliant, award-winning play, King Charles III, has come to the Oxford Playhouse after sell-out runs at the Almeida and in the West End. It's quite simply a must-see. Original, dark and intensely witty, this is a "future history play" that explores the constitutional crisis provoked when the future King Charles refuses to give royal consent to a bill restricting freedom of the Press. The consequential dilemma, both political and moral, provides a rich and gripping drama.

Bartlett pulls off an inspired coup in casting the play in the mould of a modern Shakespearean history play, written in blank verse and laced with echoes of the bard that tease the audience much as in Shakespeare In Love. We have the ghost of Diana telling Charles he will be "the greatest king", for instance, and delicious parodies of Shakespearean figuration and metaphor. We have laugh-out-loud moments, too, such as when the king compares frozen dinners to home-cooked organic meals.

This is a majestic production, in keeping with its subject. It has been developed and updated since I saw it at the Almeida - with forward references to baby George, for instance - and the impact is, if anything, greater. From the opening scene, Rupert Gould's music thrusts us into an acoustic soundscape that would rouse a spirit of patriotism in even the most hardened republican. Robert Powell as Charles, despite his physical dissimilarity to the real person, carries the show, while Richard Glaves wonderfully played for comedy Harry's chaotic charm. Jennifer Bryden delivered a stand-out performance as Kate - composed, forthright and subtly manipulative. Even the moments when we seemed faced with cardboard cut-outs of the true royals, the cliché was turned to comic purpose.

As with the best satire, a core of steel runs through the play. It poses deep questions, touches raw nerves. The kebab vendor voices the anxiety of the nation, asking "When does Britain get so cut down that it's not Britain anymore?" There could hardly be a more topical question on the eve of the referendum.