Must see: People, NT: Lyttelton, London SE1

The nation's trust deserved by an acutely preserved wit

Questions about the purpose of preservation are raised in Alan Bennett's highly entertaining new play, which takes an outrageously funny swipe at the National Trust.

Frances de la Tour's splendid Dorothy – peeress, ex-model, recluse – is as grand and down-at-heel as the decaying country house in South Yorkshire where she lives with her lower-class companion Iris (Linda Bassett).

Dorothy's brisk sister (Selina Cadell) wants to hand the place over to the trust, but Dorothy rents out the hall to a porn film company, whose shoot of Reach for the Thigh is the farcical high point of Nicholas Hytner's well-judged production.

Elsewhere, there is spirited knockabout in the contest over values between Dorothy and a National Trust man who, in Nicholas le Prevost's amusing performance, is all bristling enthusiasm for widened access. Bennett's talents for challenging cosy English complacencies are in a healthy state of preservation.

(020 7452 3000; to 2 April