Those were the days when Northern Ireland could lay claim to producing – for some time, at least – the most vital punk rock known to humankind. "New York had the haircuts, London had the trousers, but Belfast had the reason," said Terri Hooley, the man behind the Good Vibrations record shop and label.

Now it's all been repackaged as a four-disc CD/DVD box set, centred on the music as much as the superb titular documentary by John T Davis. The result is a clear window to the past. While the music staggers from the dynamic and noteworthy (including The Undertones, Stiff Little Fingers, Protex, Ruefrex, The Outcasts, The Moondogs, Starjets, Big Self, Dogmatic Element, and Rudi – although, inexplicably, their victorious single, Big Time, isn't here) to the routine (across almost 75 tracks there are too many to list, though Duggie Briggs Band's Punk Rockin' Granny is a notable low point).

Davis’s 50-minute film that truly captures the mood of change, excitement and environment. Of course, by the time it came out in 1979, London and New York had already changed trousers and haircuts. For a little while longer, however, Belfast and other parts of Northern Ireland held firm to, at very least, the notion of purpose.