The movie had an unconventional shooting schedule. Tom Hardy filmed his part in 6 days, shooting the movie twice per night as it was filmed in a single take. The other actors were in a hotel room, speaking on the phone with Hardy, who was on location.
The BMW used in the film is installed with a "low fuel warning" alert and would make a noise whenever the car was running out of petrol. The noise disrupted Tom Hardy's performance during takes, but director Steven Knight kept the actor's frustrated reactions in the movie and substituted the car's noise with "you have a call waiting" instead.
To spice things up and keep Tom Hardy on his toes, director Steven Knight would tell new things to the actors on the phone to incorporate while shooting the scenes. For example, for some takes he told Ruth Wilson, who plays Katrina Locke, to play her character like she wanted to kick Ivan from the house for a while and now she finally had the opportunity.
Locke is a dialog-driven chamber play consisting of one continuous scene. With the exception of Ivan getting into his car at the beginning, a short overhead shot of the motorway midway and a brief pan-out at the end, the entire movie takes place inside Ivan's car.
During Ivan's drive to London there were 36 phone calls. 13 outgoing, 21 incoming, 1 ignored call and 1 went to voice mail. At least half the calls ended with Ivan being hung up on or Ivan hanging up on the caller.