Everything you first see says cinema: the usherettes with torches, the faded plush-and-gilt splendour of the auditorium, the slightly altered BBFC certificate declaring Brief Encounter, 'suitable for the incurably romantic'. But this, as the marquee insists, is 'Not the film!' and not-the-film is what Knee-high Theatre serves up, always entertainingly, often delectably, sometimes sublimely.

The Cornish-based company, masters of the ensemble show, clearly have a hit on their hands: the run has been extended; transfers are talked of; Hollywood producers have been spotted. Brief Encounter is the latest successful addition to that bizarre modern hybrid: the play of the film (think The Producers, Dirty Dancing, Hairspray - though perhaps not Gone With the Wind).

Here it is the play of the film of the play. Adapter/director Emma Rice has used Noel Coward's original 1936 one-acter Still Life, which pays almost as much attention to the station staff at Milford Junction as to the middle-class lovers, alongside David Lean's 1944 film, whose focus is firmly on the repressed romance between 'ordinary' housewife Laura Jesson (Naomi Frederick) and dashing young doctor Alec Harvey (Tristan Sturrock).

To this, Rice has added nine of Coward's songs, a lot of badinage, some balloon-folding and quite a lot of film. The moment when Laura leaves her seat in the cinema auditorium and steps through the screen to appear instantly on film in her own living room is one of those moments of theatrical magic for which Kneehigh is rightly famous.

I'm less sure about the backdrop of crashing waves. Indeed, Rice's conjuring up of the legend of the Selkie, half-woman, half-seal, whose passionate nature can never be realised in human existence, is symptomatic of the production's tendency to throw a little too much into the pot.

In the process, we lose the very English tragedy of Coward and Lean's Brief Encounter 'not to mention some of Coward's finest dialogue, which featured in Laura's heart-wrenching voiceovers (remember the 'pollarded willows by the canal'?). But we get in its place an evening of wry, affectionate, hugely inventive and frequently moving theatrical exuberance, performed by an extremely talented cast - Amanda Lawrence as waitress Beryl deserves particular mention which owes as much to Dennis Potter's The Singing Detective as it does to Coward or Lean.

Booking to 22 June: 0871 230 1562