The Best Of Friends, Hampstead Theatre, London <!-- none onestar twostar threestar fourstar fivestar -->

Theatre critics often use the word "civilised" as code for "literate, humane, but undramatic". It must be said that, by that token, Hugh Whitemore's 1988 play is quintessentially civilised.

The piece explores the friendship between George Bernard Shaw, Dame Laurentia McLachlan (a Benedictine nun who became the Abbess of Stanbrook) and Sir Sydney Cockerell, the director of the Fitzwilliam Museum in Cambridge, who arranged their first meeting when Shaw was in his late sixties and Dame Laurentia a decade younger.

GBS admiringly characterised Dame Laurentia as "an enclosed nun with an unenclosed mind". Her way of life, though, made meeting hard, and their friendship, which lasted 25 years, was conducted mostly by letter. The piece recasts exchanges in the correspondence as dialogue, interspersed by diary extracts, with the last survivor, Sir Sydney, acting as our guide.

The natural home for the piece is radio. Stage treatment - with the characters reciting chunks of epistolary prose at one another on a cosily cluttered, William Morris-papered set - involves pretending that an intelligent, witty, quietly powerful anthology of mutual preoccupations (religious belief, the mystery of friendship, the meaning of freedom) can constitute a play. "Plot has always been the curse of serious drama, and indeed of serious literature of any kind," declares Shaw. The Best of Friends belies this verdict.

The piece is revived by James Roose-Evans in a warm, elegant production that casts Roy Dotrice as Shaw, Michael Pennington as Cockerell, and Patricia Routledge as Laurentia. The performances have richness and depth, but I can't help feeling that these distinguished actors could have captured the essence of the trio in a reading, without having to dress up in false beards and wimples. As Routledge trips in and out of the French windows with baskets of fruit and flowers, it looks as if the two men (Cockerell an atheist; Shaw a creative evolutionist) have employed the Mother Abbess in The Sound of Music as their gardener.

However, Pennington conveys, with great skill, how notching up friendships answers the same compensatory need as collecting manuscripts for the name-dropping Cockerell; Routledge's Laurentia radiates beatific joy; and Dotrice brings out the sensitive side of Shaw, as well as the mischievous one.

To 1 April (202-7722 9301)