They don't make celebrities like they did back in 1955, when screen icon Marilyn Monroe personally intervened to ensure that Ella Fitzgerald became the first black person to play the famous Mocambo Club in Hollywood.

Even today, when a black candidate leads the race for the US presidency and racism is largely in retreat, the little-known friendship of the black jazz diva and white Hollywood sex goddess makes for an absorbing piece of theatre.

Chicago-born playwright Bonnie Greer, daughter of a Mississippi sharecropper, understands what it took Ella to rise from a ghetto orphanage to stardom, and what it must have taken Marilyn to compel a segregated LA nightclub to hire Ella.

British jazz lovers, raised on magazine exposés about their heroes, also know about US racism. About Billie Holiday, entering theatres via the back door while the Artie Shaw band walked in the front. About Dizzy Gillespie, ordered out of the swimming pool of Dallas's biggest hotel because of "a private party in progress". And about Charlie Parker and Thelonious Monk designing music white men couldn't steal.

We sense the bitterness beneath the bright soliloquies and tuneful songs of the first act, when Wendy Morgan, a convincingly neurotic Marilyn, twisting glamorously on her chaiselongue, and Nicola Hughes, a subtly damaged Ella, happy only when the music starts, complain about their careers.

Separated by clever lighting and a transparent screen between front and back sets, their stories barely hang together at this point but after the interval the real dialogue begins and theatrical lightning starts to flash.

Very nervous when they meet ("Can I pour you some water?" asks Ella. "No, no," cries Marilyn, "your people have endured so much slavery already!") they come to realise how much they share - adulation and fan-worship, but also bad things like loneliness and an odd ability to show the public things they can't have.

Nicola's singing voice is stagier than Ella's ever was, and a drummer would add snap to Warren Wills's trio, especially in the nightclub scene, but these are minor carps about a touching and thought-provoking evening.

Until 15 March. Information: 020 8534 0310.