One movie causing a stir at the London Film Festival is Lynne Ramsay’s You Were Never Really Here, not to be confused with I’m Still Here, even though both films feature Joaquin Phoenix in full-on beardo mode.

Looking less like a phoenix than a dishevelled crow, he plays a tormented hitman with a penchant for hammers, lives with his mother and becomes embroiled in the case of a missing girl. Though it has shades of Psycho, Taxi Driver and Henry: Portrait of a Serial Killer, this is a Lynne Ramsay film through and through, featuring the unique and uniquely disturbing hallmarks of the stellar We Need to Talk About Kevin; disconcerting editing and a disorienting use of time; a stark aversion to any form of exposition; a haunting appropriation of an innocuous song, in this case “I’ve Never Been to Me” by Charlene, which I already associated with bloodshed to some degree.

And while there is bloodshed, the true terror comes from Ramsay’s psychological direction, Joe Bini’s intelligent editing and Jonny Greenwood’s striking score, planting seeds of horror in our heads and letting our imaginations do the rest. We never really know this man’s past, or his present for that matter, and the film works not in spite of but because of this. Because as anyone who’s ever been alive will attest, knowing what’s going on is often overrated. As with Taxi Driver this is more an exhumation of a tortured psyche than a conventional thriller, and Phoenix, surely one of the greatest living actors, is outstanding in a role that’s so physically and emotionally demanding.

As bold and chilling as it is violent and visceral, this lean, mean nightmare machine clocks in at just 85 minutes. Which answers the age-old question of what Stanley Kirk Burrell meant by “hammer time”.