If you count value for money in the theatre as pence per minute then the unexpected man is certainly expensive.

It comes in at around 80 minutes but there is no interval.

But if you count value in terms of performance then it comes in cheap as you get two superb and sparkling performances from Peter Bowles and Sian Phillips.

This two-hander comes from the pen of Yasmin Reza, author of the West End hit Art.

What little action there is takes place on a train travelling from Paris to Frankfurt.

Sitting opposite each other are Paul Parsky, a writer on the way to his daughter's wedding, and Martha, an attractive widow who just happens to be a passionate fan of the writer with a copy of his latest novel in her handbag.

Paul is cynical and bitter. He doesn't care for the man who will become his son-in-law although all he knows about him is that he is in his 50s and apparently has a droning voice.

For the first hour of this short play all we get is each character's internal thoughts. Only in the last ten minutes do we get any interaction between the two.

You have to pay close attention to the words in this play, which has been translated from French by Christopher Hampton and, on an evening as warm as the opening night, such concentration calls for much effort.

Principally the play is two monologues about the ageing process, about relationships or the lack of them, about literature, about love and about life.

On a lighter note Paul ponders on his digestive system, having been told by his doctor not to eat All Bran, while Martha is pleased to have found a new hair colourist to get her blonde locks just right.

But mostly the pair's thoughts are bittersweet and the lines have a good mixture of wit and comedy and contain some acute observations on life as it is lived and as we might wish to live it.

On a comparatively bare set of just six stark trees and some transparent chairs, the play constantly teeters on the edge of pretension but is relieved from philosophical tedium by the splendid delivery of Bowles and Phillips, who bring the whole show brilliantly alive and keeps its feet firmly on the ground.