Johnny Depp likes to inhabit a character. This used to be a force for good; Edward Scissorhands, Fear and Loathing in Las Vegas – those were the days. But in recent years that instinct has proved disastrous, like a sex addict who doesn’t respond to the word “no”. The Lone Ranger, Dark Shadows, Alice in Wonderland, Mortdecai: the sum total of all the gurning and broad shtick in this black mass of affectation has been profound despair – a feeling in the pit of the audience’s stomach that Depp, an actor they used to enjoy, is now a byword for monstrous self-indulgence. Perhaps the only way out was for the one-time risk taker to play a monster.

In Black Mass he’s notorious Boston kingpin James “Whitey” Bulger, a malevolent, unhinged psychopath and study in carefree sadism. Despite conspicuous transformative makeup and lighting that isn’t quite good enough to hide it, it’s a decent performance – one that grows on you as the movie goes through its brutal, matter-of-fact paces. It’s still Depp performing under there, plying his trade in the least subtle way imaginable, but maybe Scott Cooper did a Nicholas Meyer and bored him into a more natural performance with take after take like the latter did with William Shatner in Wrath of Khan. The result’s unsettling. It’s also, despite the near total absence of humour, a funnier movie that anything Depp’s made in a decade. Bulger was a cruel killer and an ally of Irish Republican fascism but it’s not all bad, he gave us Johnny Depp back.

Mass tells the shocking story of Bulger’s rise from local thug to South Side crime lord using the time honoured, Scorsese patented device of mobster flashback. As his former confederates spill their guts, we’re treated to a hard lesson in the corruption at the heart of the American dream; a land in which anyone can make it, provided their childhood friend’s an FBI agent looking to make a name for himself and their brother’s a charismatic state senator. With that sort of advantage you can be recast as the lesser of two evils; preferable to the Mafia and a reliable source of information on the bureau’s top targets, rather than the mercenary, deranged, clichéd-hypocritical lover of old ladies and his mother, who doubles as the killer of a young woman and just about anyone else responsible for a slight – real or imaginary. It’s worse for knowing this is a sanitised version of events; a movie that stands back or looks away during the worst moments, content the underlying threat is enough; a movie that paints out the excesses but nevertheless leaves you smarting from the company of a damaged street fighter who was untouchable until the FBI finally woke up to the obvious and started indicting its own – a process the movie tells us took twenty years.

Cooper’s film deserves attention; it’s biography scored like a horror movie and shot dispassionately. The performances do the talking. Depp, methodical and confident here, does a fine job of radiating menace in every scene he bestrides. His Bulger is a man who commands absolute loyalty, yet forgot to keep his own people on side, making them feel threatened, while making it clear he’d be more than happy to violate or kill their wives and girlfriends. Little wonder then, that Bulger eventually ended up on the run. Now caught and able to watch this movie from his jail cell, he’d probably find it a lot less glamourous and explicit than Ray Liotta’s counterpart did when eying Goodfellas. That’s both a regret and a recommendation. Funny old world.