Rocky II contains the flaws of the original: simplistic characterizations, saccharine romance, a tendency to cuteness. But it also fills the heart and quickens the pulse.

By the punishing heft of the big fight, there is the clear hint that the series will soon plunge into an unpalatable patriotic fervour. For now, though, with its leathery texture of working class Philly-life it felt enough like reality.

Stallone and producers Irwin Winkler and Robert Chartoff know from experience audiences love to root for the underdog and have concocted an irresistible final 30 minutes.

It didn’t really need to be made – a problem that countless sequels must deal with.