Olivier, National Theatre, London Critics attempting to characterise the regimes of different artistic directors of the National Theatre have often alighted on their attitudes to the work of Alan Ayckbourn, whose plays – hugely popular but also structurally experimental – are a useful test case for where the line lies between subsidised and commercial theatre. An unofficial house dramatist under Peter Hall and Trevor Nunn, Ayckbourn was featured little by Richard Eyre and seemed to have been dropped completely by Nicholas Hytner. However, late in his reign, Hytner commissioned a successful revival of the Christmas comedy Season’s Greetings and now, in honour of Sir Alan’s seventy-fifth birthday this Easter, comes a new staging of one of the hits of the Hall era: A