In the hands of director Alex Cox, a potentially tacky melodrama is transformed into a tragic nightmare of muck, pain, and addiction. Sid & Nancy is often a miserable and even difficult watch, but its treatment of its subject matter feels unique among musical biopics.

London, 1977. Following their breakout success in the UK, punk band the Sex Pistols are preparing to tour the USA. Bassist Sid Vicious (Gary Oldman) meets Nancy Spungen (Chloe Webb), a herion-addicted groupie, and together they embark on a doomed romance that destroys the band, their relationships, and ultimately their lives.

It is not a spoiler to state that Sid & Nancy ends with Nancy dead and Sid charged with her murder. Cox’s film begins at this point, and then tracks back 12 months to showcase the events that led the lovers to the New York hotel room. It is an understandable plot structure – the audience of the time were well aware of both the Sex Pistols and Spungen’s death – but it gives the film a grim and inevitable trajectory. After the prologue, it is a continuous downhill road from start to finish.

This is not how a typical musical biopic is supposed to work. They typically follow a pattern of difficult childhood, initial success, drug addiction, and then redemption. It’s a model that forms the plot of Taylor Hackford’s Ray (2004), James Mangold’s Walk the Line (2005), and F. Gary Gray’s Straight Outta Compton (2015), among others. This is not a pattern that Cox follows: he deliberately begins Sid & Nancy at the height of the Sex Pistols’ success, skipping both the childhood and initial success portions, and heading straight into the addiction phase with no redemption in sight. It makes for bleak but effective viewing.

Oldman and Webb are excellent in their lead roles, as is David Hayman as the Pistols’ manipulative impresario Malcolm McLaren. It is all tremendously well shot as well, thanks to an early-career Roger Deakins. The real achievement, however, is Cox’s. It is an easy story to sensationalise. It is also an easy story to make unremittingly depressing. Punk is an easy movement to mock and ridicule. The screenplay, by Cox and Abbe Wool, avoids each and every pitfall. It feels respectful of the real lives involved (Vicious’ mother participated during development, Spungen’s parents did not), it contains well-based moments of levity and humour, and comes from a place of personal experience in the English punk scene.

It also maintains a close and personal scope: it is not a film about the Sex Pistols, nor is it an expose into the driving forces behind punk or its key players. Cox has directed a tragic love story. That it is situated within this broader historical context adds depth and detail, but ultimately failed romance is what dominates. That also sets it out, rather brilliantly, from the constant stream of musical biopics that emerge each year. This is arguably Cox’s finest film. It’s arguably one of the United Kingdom’s finest.