But he also ensures that the reality of torture isn’t forgotten with a final image that leaves one in no doubt that misplaced authority can be very dangerous indeed.

Though written in 1958, it only received its first production in 1980, and the weaker moments of this early work benefit enormously from crack casting as the head of an unspecified institution finds himself undermined – and with good reason – by his subordinates.

It’s Christmas and one of the numbered (never named) inmates has been found dead whilst another has just given birth.

The always excellent Simon Russell Beale’s ex-colonel Roote, eyes bulging furiously, extracts every ounce of comedy from the script, squirming one moment, blustering the next, and John Simm’s ambitious Gibbs is the epitome of creepily controlled efficiency, each measured word and movement a calculated step in his plan to supplant him.

John Heffernan’s aptly named Lush gets soused in more senses than one, whilst Indira Varma’s provocative, sexually indiscriminate Miss Cutts lures underling Lamb (Harry Melling) into the sacrificial chair to sample the brutal treatments this so-called “rest home” dishes out to its unseen patients.

Trafalgar Studios
Whitehall, SW1A 2DYTube
Tube | Charing Cross 
Until 3rd August   £10- £54.50

Photo: Johan Persson