Produce an ending that is both ingenious and unexpected in this type of Sleuth-like thriller and you have cracked it. The audience will leave the theatre happy, talking animatedly about the surprise that has been sprung on them at the last moment and rapidly forget most, if not all, of the play's defects. Actor Roger Rees and Eric Elice, the authors of this slight but entertaining piece, conclude the proceedings with a coup de theatre that will, I reckon, fool most people. This is a doubly surprising as most of the content of this thriller is hardly novel, containing all the expected elements of the unexpected that one associates with the genre.

Palace artistic director Leon Rubin, in his last production before leaving Watford to take charge at the Bristol Old Vic, ensures in his staging that nothing is quite what it appears. He is aided enormously by his cast, namely Roger Rees himself and Jane Lapotaire.  Here we have a pair of actors more usually associated with classical roles but who are well able to pull the wool over our eyes playing people who rarely tell the truth. Lapotaire is the glamorous lady who invites Rees’ disgustingly dirty tramp, sporting a filthy coat and outrageous Scottish accent, into her posh London apartment and offers him a vast sum of money to impersonate her dead husband for reasons I won’t divulge. In fact to reveal more would be to risk being labelled a spoilsport by breaking the unwritten rule that critics should not give the game away and spoil the surprise. Double Double may not be a classic of its kind but it is an amusing diversion.