The Mountaintop, Theatre 503, London

The strange last night of Dr King

What was Martin Luther King's last night on earth like? What was he wearing, what was he doing and who was he doing it with?

In the American playwright Katori Hall's new play, The Mountaintop, he was in the company of Camae, a very cute black maid from Memphis. She's responded to a call for room service; coffee and cigarettes to help King's next speech along. It's the first day of her new job.

Pastor King is finding his own job a bit trying. He's just come back from delivering a speech on the plight of sanitation workers at the Mason Temple in Memphis; it's pouring down with rain and he's stuck in a damp motel room. He's also been hounded by assassination threats.

It is a testament to the pull of The Mountaintop that it's a thrill to be stuck in that room with Camae and King, witness to the wild imaginings that Hall had when she conjured this relationship set during King's final night on earth.

It is a relationship that is breathtaking, hilarious and heart-stopping in its exchanges and in its speedy ability to reveal character and pull the audience into the ring. One minute the Pastor and his new friend are beating each other up with rounds of oratory; the next, they're trying out how to look sexy while smoking. We discover, too, that King has stinky feet, wonders whether his moustache looks good on him or not and has an eye for the ladies. We also learn that he is terrified. Terrified that he is about to die, that the attempts on his life will finally get him. Terrified that he hasn't had the chance to fix the world and that he hasn't said goodbye to his wife and children.

The Mountaintop is an imaginative portrayal of one of the most famous men who lived, whose dream of equality made his 39 years of life resonate long after his assassination. While Hall doesn't give King his dream in The Mountaintop, she does give him another one; one that is wondrous, hilarious, and heartbreaking to witness. In this world premiere at Theatre 503 – we get it before New York does – her writing gets the actors and director – James Dacre – that it deserves. David Harewood, as King, is going to be on screen in a new BBC drama as Nelson Mandela soon, and on this showing, it will be well worth watching; his mighty grip on character – and the swing between fear, humour and quietness – reminded me of Forest Whitaker's turn in The Last King of Scotland. His sidekick, Lorraine Burroughs, is beautiful, sassy and worthy of the company she has been sent to keep. No wonder King wants room service to last longer than it should.

The pair deliver from the stage of a tiny theatre to a small audience who watch their exchanges transfixed; these two are on fire. Katori Hall must be ecstatic that her words have been executed in the manner that they have.

To 4 July (020 7978 7040; www.the mountaintop.co.uk )