Spencer Tracy, one of the most natural actors to have ever stepped in front of a camera, gave three pieces of advice to every young hopeful who asked for his secret: “Show up on time, know your lines, and don't bump into the furniture.” Sometimes he’d throw in a fourth, which outlined what he saw as the proper relationship between the audience and the film actor’s craft: “Never let them catch you at it.”

Tracy died in 1967, though his words still bear repeating today, ideally through a megaphone outside Jared Leto’s trailer. In preparing to play Batman’s nemesis The Joker in the forthcoming comic-book movie Suicide Squad, Leto got himself into character partly through a series of in-character tricks and stunts, which were widely described as part and parcel of the 44-year-old Oscar winner’s method acting approach.

One involved sending cast members sex toys, used prophylactics and pornographic magazines flecked with what was hopefully glue. Leto required the crew to address him as Mr. J during the shoot – J for Joker rather than Jared – while after hours, he tormented the actor playing his henchman with phone calls throughout the night.