There is more warmth and joy in Sean Penn’s portrayal of the San Francisco politician and activist Harvey Milk than there has been in his past ten years of roles put together. In this affectionate biopic, Milk, the first openly gay man to be elected to public office in the US, is depicted as a pied piper and a merry prankster; a father figure to every stray teenage street hustler with the scars of an unhappy childhood still raw.

His is a face that seems permanently on the verge of creasing into a thousand laughter lines. He’s one of those lucky few whose articulacy is honed by anger; his opportunistic cruising is tinged with compassion like a hug that draws every lost soul in the Castro neighbourhood under his wing.

The device of having Milk narrate the story of his own life is an effective means of driving a story that could otherwise have been a rather episodic list of events. The director Gus Van Sant has Milk dictate his autobiography into a tape recorder, to be played only in the event of his death by assassination — an eventuality that tragically came to pass.

Van Sant’s attention to detail is meticulous, from the authentically nicotine-stained 1970s colour palette to the fastidious recreation of Milk’s shop front in the very same store it used to inhabit; the ludicrous facial hair to the unfortunate polyester shirts. It’s a fashion horror show but the vital spirit of 1970s San Francisco vibrates through every frame.

Most effective is the creative use of archive material. The opening credits role over news footage of police raids in Greenwich Village gay clubs in the 1960s, showing the covert and shame-filled world Milk had previously inhabited. His move to San Francisco in the 1970s is illustrated with more archive footage, woven virtually seamlessly into the story.

For his supporting cast Van Sant draws upon both awards darlings and a few more unexpected names. Emile Hirsch, who previously caused a stir in Penn’s Into the Wild, is terrific as the campaign’s denim-clad dynamo, the hustler turned radical Cleve Jones.

And Josh Brolin’s star continues to rise after a remarkable and diverse run of roles, including President George W. Bush in Oliver Stone’s W. and the backwoods cowboy Llewelyn Moss in the Coen brothers’ No Country for Old Men. Brolin brings a complexity and an almost childlike innocent petulance to the role of Dan White, Milk’s colleague and, ultimately, his murderer.

Van Sant has also trawled mainstream multiplex cinema for talent. Lucas Grabeel, from High School Musical, appears, playing a rather peripheral figure. And James Franco graduates from stoner comedies with a finely judged turn as Milk’s former partner Scott Smith. Slightly less successful is Diego Luna as Milk’s highly strung lover Jack Lira, a performance permanently pitched a couple of notches above strident hysteria and which gets a little wearing.

This is a more conventional film for Van Sant, whose recent work — Elephant, Last Days and Paranoid Park — has tended towards a more opaque, impressionistic approach. But while he may have reined in his more experimental urges, Van Sant’s skill as a film-maker is showcased here to inspiring effect. Rarely has a lesson in political history felt so involving and alive. What’s more, it’s a genuinely important film that could not be better timed.

15, 128mins

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