The play flits between 1940 and the present, where Raymond's wife, Sophie (Amanda Mealing), is now a widow. Over 60 years, before she went into an old people's home, she kept a daily journal of the garden's flowerings. During this time she missed just three months in the summer of 1940, a period that coincides with a visit by a Czech refugee. Enter Leonora, the biographer from New York, a character who teeters on the brink of being a cliche despite the best efforts of Jan Waters. While she puzzles over what happened to Raymond and the other people in the house during those three months, Sophie's vague and repressed son, William (Chris Matthews), undertakes his own reconstruction of the past. From weather records, he tries to plug the gap in the garden journals. This is a task he foolishly describes as not an art but a science. Foolishly because Moffat's play is full of little warnings about the dangers of interpreting history - whether that history is private or public. Several of these come in the form of pictures. A photograph of Raymond's father appears to show him at Ypres, whereas he actually died of measles in Bedford. Leonora describes a painting of Robert Louis Stevenson in which a perfectly rolled cigarette has been painted out and replaced by a less interesting but more worthy pen. Inspired by a statue in Winchester Cathedral, Raymond has written a poem about a Mr Walter, the diver who in 1906 saved the cathedral from destruction after its foundations flooded. Yet (as Leonora reveals) the face of the statue is not that of the real Walter.
And if history can play tricks with the past, how much more so with the future. Raymond, a manic-depressive alcoholic, has convinced himself his poem "The Divers" is rubbish: in fact, it becomes the monument by which he is remembered.
With little touches like these, Moffat shows how adept he is at threading an argument through a play but, though the structure of The Blue Garden is impressive, some of its nuts and bolts are missing.
In his dazzlingly accomplished first stage play, Iona Rain, Moffat displayed a sharp wit but also commented upon the uses of wit as a weapon and a defence. In Iona Rain, four ex-public schoolboys, now in their thirties, are reunited on a Scottish island and it soon becomes clear that their repartee disguises a range of emotional handicaps. "I think wit is an overrated virtue, men use it to control the conversation," says the wife of one of them, putting her finger on the problem as only an outsider can.
In The Blue Garden, Moffat has himself fallen into the trap of trying too hard to be clever. The play does boast some well-crafted one-liners ("I had you down as a bookish type, but all along you're just Ted Hughes," exclaims Leonora when William appears with a dead rabbit and a shotgun). Too much of the dialogue, however, consists of speeches full of little rhetorical flourishes, as if the characters weren't talking to each other but addressing the Oxford Union. Robert Reynolds's linen-suited Raymond adds to this impression by delivering most of his lines to some distant point over the audience's heads.
To 27 July (0181-680 4060)