When Marilyn met Ella, not a lot happened. This does not prevent Bonnie Greer concocting a paper-thin, woefully un-theatrical and clumsily written two-hander based on the fact that Marilyn Monroe insisted on raising the colour bar at the Mocambo nightclub in Los Angeles in 1955 so that Ella Fitzgerald could sing there. She sat in the front row for the week-long engagement and took all the publicity flak in her stride and her shimmy.

To call this a musical drama (as Greer does) would be to insult more or less everyone from Wagner to Sandy Wilson. The first half is a pair of unrelated, intercutting monologues with Ella bemoaning her life on the road in a recording studio and Monroe writhing languorously around New York while wanting to be taken seriously: “I just wanted to tell you,” she shouts at an unseen Arthur Miller, “I did finish reading Ulysses.”

The point is that Marilyn was no superficial airhead and Ella not much of a career go-getter; Ella’s opening song, “Someone to Watch over Me,” seems to invite the sort of guidance she lacks. But then Nicola Hughes rips into “The Lady is a Tramp,” and I’ve no idea at all what that is meant to signify (Ella wasn’t one), apart from “sit back and enjoy.”

That line of least resistance pays off when the second act moves to the Mocambo (two large painted parrots glide in from the wings) and the upstage curtains part to reveal the musical trio led, with great distinction, by Warren Wills at the piano. Hughes reels off a few more numbers, including a knock-out “Mack the Knife,” Marilyn begs her to sing one for her alone (“My Funny Valentine”) and they go up on the roof.

At least the characters are now inter-acting but Marilyn just spews pious clichés and banalities about having to stand up for yourself in the film industry, while Ella bridles a bit at being talked to in such a way before eulogising Marilyn as a woman ahead of her time.

Hughes sings gloriously all night. That’s one plus. The other is the simply sensational performance of Wendy Morgan as Marilyn, a feat of stunning physical evocation without a hint of hollow impersonation. Terry Johnson may have made Marilyn look better than she was, and even funnier, in her showdown with Albert Einstein in his brilliant Insignificance.

But Morgan conveys a world of sighs, shudders and sheer physical enchantment with a script you should start that late winter fire with. The transcendent Miss Morgan has been away from the stage for too long. Can someone make it more worth her while next time?

- Michael Coveney