Welsh concrete expert Locke (Tom Hardy) discovers his life unravelling as he speeds down the fast lane of the M1. He's deserted a major building project in Birmingham to be by the bedside of a one-night-stand while she gives birth to his baby in London. At the same time he's got to break the news of his transgression to his wife and children while fending off his furious boss. An unexpectedly tense drama completely played out by bluetooth phone behind the wheel of a car.
Most thrillers tend to follow a fairly rigorous formula. More often than not, it's a murder or crime that triggers the thrills; perhaps a web of conspiracy that goes all the way to the top; most likely a trigger-happy hero at its centre.
Locke is not most thrillers. Its titular star, Ivan Locke (Tom Hardy), is an ordinary working stiff. He is married with kids. He works in construction and obsesses over cement. He speaks in a gentle Welsh lilt. He wears a fetching bit of Laura Ashley knitwear. And he spends the entire duration of the film in the front seat of a BMW X5, driving the 120-mile journey from Birmingham to London, never once threatening the speed limit.
On paper, Locke sounds dull and pointless. On the screen, it's unfailingly gripping, an intriguing experiment in minimalism and suspense. Like Buried or Phone Booth, the fixed location means thrills come not from gunfights or combat, but frantic phone calls and methodical plot developments. Yet the experiment seldom trips over itself.
Writer-director Steven Knight's ingenious script extracts tension and excitement from the unlikeliest of places. Ivan is an orderly, stoical man, who approaches life in a calm businesslike fashion, and a single foolish mistake threatens his hard-won peace. Morsels of the drama reveal themselves slowly and precisely, layer by layer; we watch spellbound as Ivan's life collapses via his hands-free phone.
Inevitably, given the ambitious format, not every piece fits perfectly. Ivan's imagined conversations with his late father, directed to an empty passenger seat, are a clumsy device, which breaks the naturalistic spell.
But it's an infrequent stumble. Though some in the Valleys might take issue with the accent, Hardy's is a commanding, absorbing performance. Most actors would have aimed big and blustery with the part; Hardy goes small and measured, nuance from behind a seatbelt.
Meanwhile, Knight's direction - aided by Haris Zambarloukos's slick cinematography - is at once inventive and unpretentious. It's a delicate tightrope to keep a confined location visually compelling without detracting from the story, but Knight manages it - and at a running time just shy of 85 minutes, doesn't outstay his welcome.
Lean, engrossing, and entirely unique - you'll never look at junction 5 of the M1 in the same way again.