What if...? is one of imagination's great starting points? It is also one of theatre's jumping-off pads. Michael Frayn's 30-year old comedy Balmoral is set in a Britain 40-years before that, one in which the revolution happened 20 years earlier in this country and not in Russia.

There's a contemporary twist to the underlying theatrical one. Rik Maynell has had to withdraw from Alan Strachan's production on health grounds and the understudy, Steve McNeil, has stepped into the role of Skinner. It's the stuff of fiction in one way – all those "the show must go on" fantasies come to real life.

If you know Gogol's The Inspector General,/i> either as a play or in its various film guises then you know where some of the Frayn piece is coming from. The former royal retreat in the Scottish Highlands has been turned into a writers' retreat. They are squabbling and the warden is harassed. What's more, the building is collapsing through lack and maintenance and there's only one odd-jobs man to do all the work.

Our authors are all popular middle-brow writers of the period – Hugh Walpole, Warwick Deeping, Godfrey Winn and Enid Blyton. They're all conforming to the new régime – up to a point. Then a Russian journalist (bear in mind, please, that Russia is still an imperial power) and his female minder arrives to interview Walpole. There's one small problem. He's not there.

As the misunderstandings multiply, the cast show what ensemble acting can achieve, even without a star name in the cast. Jeremy Child's Deeping is the old-timer who contentedly skims the political waves, while Alison Skilbeck's Blyton makes one wonder what lurks in the undergrowth through which peep Noddy and the Famous Five. Robert Hands is the insouciant Winn, oh-so-slightly on-the-make.

As Skinner, McNeil gives a very good performance as a man who wants to play by the rules, even if he's not quite clear what they are. His worries are the stuff of his writers' mockery, but he knows that he carries the ultimate responsibility; revolutions can be hard on failure by its apparatchiks. And there's a bravura turn by Andy Gray as McNab, whose odd jobs turn out to include at least one very peculiar one indeed. A two-dimensional part turns out to provide a three-dimensional acting triumph.

Our Russian visitor is Gyuri Sarossy, so determined not to be impressed by his visit and Katie McGuinness flusters prettily as the girl with a literary crush. The set by Alexander Gilmour is a player in its own right, with the careful details of neglect mingling with the touches of an imposed bureaucracy which places its own low valuation on the creative process.

It's all great fun for its two-hour progress. A pity that the projected national tour has been curtailed. It's not Frayn's deepest play nor his most scintillating comedy. But it's still something more than a mere star vehicle.