Few 20th-century figures have fed the tendency for myths to subsume the men from whom they spring quite like Martin Luther King.
But the manner of King's departure from what the Nobel winner and clergyman considered the world of sinners, only hours after prophesying his own death, has entered folklore. His last moments have never suffered from a deficit of speculation. The night before, King delivered a speech to a Memphis church congregation during a strike by sanitation workers. His flight had been delayed because of a bomb threat, news of which infused the speech with a palpable sense of foreboding. Referring to what was only the latest attempt on his life, King told an enraptured audience that he had been to the mountain top (from the Bible's Book of Exodus, in which Moses leads the Israelites out of Egypt), and had seen the Promised Land. "I may not get there with you," he said, his cadence rising towards a climax.
He was right. Fewer than 24 hours later, he was shot in the cheek on the second-floor balcony of the Lorraine Motel (the bullet bobbled down his spine before lodging in his shoulder). King was with friends in Room 306 before his death just after 6pm. Among his coterie were the Reverend Jesse Jackson and the Reverend Ralph Abernathy, who claimed to have rushed out and found King on the floor after hearing the shot.
Surveying the wreckage of conspiracy and counter-conspiracy that surround King's death, Katori Hall, a playwright who grew up in Memphis, Tennessee, decided to alter the focus of King's death. Instead of looking yet again at the myths surrounding the final night, she decided to focus on the man who delivered the speech the night before: to substitute clarity for confusion, and insight for intrigue. Two years later, her play, The Mountain Top, is set to open at Theatre 503, at The Latchmere pub in Battersea, south-west London.
"The idea of King has been sanitised so that what we have is a toothless tiger who is glorified rather than remembered," says Hall. But remembering matters: the real King, she says, "was extremely radical, militant, antagonising, a serial womaniser, and divided within himself between different forces".
The Mountain Top looks at the hours after King, played by the British television regular David Harewood, retired to Room 306.
He is joined there by the mysterious figure of a motel maid (Lorraine Burroughs), who invites King to contemplate his prejudices and prospects. In so doing, she suggests the possibility of an alternative reality: what if King had lived? And what would that have meant for Barack Obama?
Hall, who trained as an actress and writer at Columbia, Harvard and the Juilliard School in Manhattan, has just received the prestigious Playwrights of New York Fellowship. She is completely clear about her purpose: to zoom in from the panoramic vista of King the myth to the grubby intimacy of King the man.
"Growing up in Memphis, King's photo and legacy is everywhere," she says. "I suppose a little bit of my motivation is setting the record straight, clarifying something that has become hazy. I think that matters. If you can't understand the past, you can't understand the present". And what if the man is less fun than the myth? "He's not – and he's far more interesting too," she says.
Hall's mother grew up just yards from where King delivered his speech in downtown Memphis. "My mom wanted to go, but her mom – Big Momma – said because of the bomb plot it was too dangerous. My mom always said it was the biggest regret of her life, not going". 'Mom' (said with a southern drawl) is currently trying to get a new passport in time to make sure she doesn't regret missing this show too.
At the helm is James Dacre, 25, a British director who met Hall on Broadway while he was living in New York. Dacre describes Theatre503, a re-branded 80-seat space above The Latchmere pub, as a venue "that puts the audience in the ring with King".
"The play is like a 90-minute boxing match", Dacre says. "It's intense, effectively an actor's gym". There is a focus on the single most important word in King's life: dream. "No other word conveyed what he represented as effectively. This is very much a dream play rather than a biopic, though in looking at how King dreamt we can see more clearly how he lived."
Harewood, who received plaudits for his role alongside Leonardo DiCaprio in Blood Diamond, describes the atmosphere in Theatre503 as "intense" and "more severe than anything I've done for a while". Not surprising, given he was recently seen playing Friar Tuck in the BBC's Robin Hood. The actor, who describes himself as "a little Christian", went to Barbados four years ago to make a BBC film about his ancestors who were slaves. He says he took the part to get inside the mind of his hero King, who "just edges ahead of Mandela for me", trying to get to know "the pillow-fighter as well as the politico".
Burroughs' mixed-race heritage – her mother is Irish and her father from St Kitts – and Birmingham childhood have known King's influence. "At home we used to have a poster of King's 'I have a dream' speech in the living room, so in a way he has always been there," she says.
So too has the enduring image of the mountain top. But the notion of King's "mountain top" speech as a literal or metaphorical peak is a clumsy illusion, Hall says. "We think of that speech as a kind of summit in King's life story," she says. "Yet it's an irony of King that the closer you get to him, the further you get from the orthodox view.
"The man we call a dreamer was full of nightmares too. That's why we're doing this play."
9 June to 4 July, Theatre 503, The Latchmere, 503 Battersea Park Road, London SW11 (020 7978 7040; www.themountaintop.co.uk)