The familiar adage notwithstanding, fiction is more often stranger than truth; sometimes so much so that credibility departs on wings of scepticism. That is the case with Justin Butcher's Scaramouche Jones, a one-man play that deals in dramatic exaggeration to the detriment of audience empathy.

It opens on the last night of 1999, when the eponymous circus clown comes back to his dressing room - opaquely, a large tent filled with acrobatic and other equipment - to tell us that millennium midnight will usher in his 100th birthday. He adds that he will then end his long life by suicide, presumably weary of it all.

The reminiscences begin, addressed to the audience, of his birth, in Trinidad, to a dark gypsy who sells sex for a living. Of his father he learns only that he was an Englishman. When he is six, his mother is killed, probably by an angered client, and he becomes in one day an orphan, an exile and a slave. He is owned by a Senegalese who travels over north Africa giving snake-charmer shows, helped by the boy.

The story goes on and improbably on, taking in life with Polish gypsies, an abortive marriage to a child bride, a job burying bodies in a concentration camp, a spell in Spandau prison, trial and acquittal at Nuremberg, the granting of a British passport and the start of his circus career at the age of 51. The story effectively ends there. He has been 50 years a benighted nomad, 50 years a clown; and now the void.

Pete Postlewaite plays Scaramouche without ever looking or sounding like a centenarian; indeed, he sheds years as the narrative proceeds. That need not matter too much, but he creates an impression that the character exists to accommodate his thespian skills, rather than the opposite. He projects a strong and versatile stage presence, but not enough to redeem this script, which is, perhaps, an impossible task. The play's the thing, and this one, directed by Rupert Goold, is indomitably implausible.

Runs until October 13th