Run time: 134 mins

Not even five decades can dull the spiky impact of this cinematic gem. Jack Nicholson is at his deranged best long before he even picked up the script to The Shining.

Based on Ken Kesey’s 1962 best-selling novel, Nicholson is Mac McMurphy, the subversive wildman and troublemaker, sent down for statutory rape, whose unstable behaviour gets him a transfer to what he clearly thinks will be the cushy option of the mental institution.

Mac discovers that the set term of his prison sentence has been changed to an open-ended incarceration, dependent on psychiatric assessment. So Mac leads a revolt against the spirit-crushing regime of pills and shock therapy, and against the icy control of Nurse Ratched (Louise Fletcher).

The film’s simplistic approach to mental illness is not really a fault of the film itself, because it has no interest in being about insanity. It is about a free spirit in a closed system.

It remains enduringly popular as an anti-establishment parable, and McMurphy prevails as a character, despite the imperfections of the film, because he represents that cleansing spirit that comes along now and again to renew us.