Behind The Iron Mask, Duchess Theatre, London

The show - with music and lyrics by John Robinson and a book by Colin Scott and Melinda Walker - tackles the story of the man in the iron mask, a character who is played here by Robert Fardell in a helmet that leaves him looking like a cross between Hannibal Lecter and a metalwork-class disaster. The myth of the mysterious prisoner, kept in permanent, faceless solitary confinement, inspired the novel by Alexandre Dumas and its movie spin-offs, and it continues to excite speculation about the identity of the man and the reasons for his captivity. Hard, you'd have thought, to make such a figure wholly unintriguing, but here the Prisoner exerts about as much romantic fascination as a biscuit tin with a jammed lid.

Gone is the theory that he's the twin brother of Louis XIV, incarcerated to prevent a succession crisis. Gone are the musketeers. Instead, we are offered a hermetic three-hander. Disobeying the monarch's orders, the bald, beefy, Jailer (Mark McKerracher) tries to impress the beautiful, on-the-make Gypsy (Sheila "Three Degrees" Ferguson) with his closeness to wealth and power by bringing her back to the swankily appointed cell. How, though, can she be privy to the momentous secret and expect to live to tell the tale?

Ferguson could devour the anodyne score for breakfast and still be peckish, but she fails to catch fire in her shawl-waving gypsy dance, and remains bizarrely "centred" and imperturbable, as though the fright-masked stranger were a guest with a obsessive-compulsive disorder on a daytime TV show.

The band sound as if they are not there - and who can blame them? The music occasionally rises to a pallid echo of Lloyd Webber, but the lyrics are a disgrace to doggerel and the book is a study in itself. Did I hear the Gypsy imply that she would have respected them more if they had killed her?

In the programme, Robert Fardell jokes that he is "the longtime holder of the Sports Anorak Award" and, though he has a sweet, high, singing voice, I'm afraid that when delivering dialogue, an anorak is pretty much how he comes across. No chance that the flouncy ballgown and mask that the Prisoner significantly keeps in his trunk will lead to revelations of closet transvestism. This tedious venture was summed up when the Jailer handed the departing Gypsy the pearls that will provide for her future - and missed.

Booking to 5 November (0870 890 1103)