There are quite a few good one-liners and extended jokes, but the real comedy comes from the farceur's traditional play on who knows what, and who doesn't. Most of Ayckbourn's characters are unaware of things that are very important, and most of the time we, the audience, know most of these things. We watch the characters struggle with their varying degrees of misunderstanding and unwelcome surprise.

This, not to strain a point, is a central force of Oedipus as well. The further dimension of the entire Ayckbourn trilogy is that even the audience begins to understand, when the same events recur from different perspectives, that it doesn't understand as much as it imagined - true, again, of the entire Oedipus trilogy.

However, the comparable playwright that most obviously comes to mind is not Sophocles but Chekhov. There are lots of similarities between The Norman Conquests and the Donmar's recent production of Chekhov's Ivanov; in both works, ordinary people - neither very ignorant nor very poor - find themselves somehow condemned to a life which though superficially quite pleasant, is actually almost insupportable, at least at times. Yet they seem quite unable to free themselves from their fate, even by behaving badly, in desperation - Ivanov is vile to his wife, his neighbours are nasty to each other, and Ayckbourn's family actually insult the family lares and penates by throwing biscuits at each other in their misery and fighting over a coffee pot. In the end they seem resigned to their unnecessarily unpleasant lot. It is tragic.

Yet Chekhov insisted again and again that his plays were comedy, not tragedy (though I have never found them funny), while Ayckbourn's plays are clearly much more than comedy, though clearly they are funny. Pigeonholes are problematic.