But whatever headlines DiCaprio’s involvement made in 1997, it's impossible to imagine anyone else but Christian Bale as Bateman.

“I think what Mary saw in him was a kind of focused narcissism,” said producer Edward Pressman. “And he himself understood how this role could change his career – and it did. He went after it with a vengeance.”

The Welsh-born actor was certainly hungry for the part. “People told me it was career-suicide,” he says. “But I thought, ‘Yes, I want to do it.’”

It became the first of his now familiar physical immersions in a role – whether dropping 63lbs for The Machinist, beefing back up for Batman Begins or swimming through leech-infested rivers for Herzog in Rescue Dawn.

When Harron suggested Bale work out, Bale hired a trainer and sculpted his body into the kind of six-pack buffness normally only found in Calvin Klein underwear ads (“You can’t play Bateman and have a beer belly”).

He had bleached his teeth (to get a “Tom Cruise smile”). He even hung out with Wall Street brokers (“Most of them knew the book backwards... I asked them what I should look at and they said, ‘Go rent Wall Street’”).

When Harron sent him home with a group porno VHS – research for Bateman’s preening, three-way sex scene set to Phil Collins’ ‘Sussudio’– Bale returned with a clutch of stick-figures drawings showing ideas for different positions.

Next: Playing It For Laughs...