The lights in the venue have blown – again – and the stage is cast in the sickly green glow of the emergency back-up.

It couldn’t be better for this brilliantly bleak, bone-dry mental health comedy, which suggests the boundaries between patient and doctor are often more blurred than we might imagine.

Lee Fenwick is the character comic behind unemployed shipbuilder Mick Sergeant and he brings a similarly compelling blend of pathos and bluster to Dr Benoit, a dubious psychiatrist trialling rock 'n' roll as therapy for depressive patient Rachel (Rachel Lancaster).

But while Fenwick is good, it’s Lancaster who’s the star of this piece, delivering the show’s best lines in the world’s most unrelenting monotone. Though it challenges the energy levels, her morose takeover of Dr Benoit’s upbeat Mood Elevator song (“Going…down”)and pitiful list of goals (“Don’t kill self”)make Rachel one of the most weird and watchable characters about.

For the pessimistic of outlook, this off-kilter medley of quiet desperation and deadpan wit is just what the doctor ordered.

Just The Tonic Up The Stairs, 260000, until Aug 26 (not 14), 12.55pm, £5 - £6.