Julia Roberts

Julia Roberts had one problem making the romantic caper The Mexican. She had to pretend she was in love with screen heart-throb Brad Pitt.

The off-screen friends laugh about finally having to play on-screen lovers.

"It was a daunting challenge at first, but there's a familiarity that comes with the two of us," says Roberts. "We had a short time to convey a lot of years together.

"The truth is Brad's lovely. Sometimes you get on a movie set and people change, but he's great."

Pitt adds: "Julia and I had been looking at working together for years, we'd circled around a couple of projects, but nothing happened before this."

In fact the two stars actually don't spend that much together in the film which has Pitt cast as a small time crook who isn't really cut out for a life of crime.

He accepts the job of going to Mexico to retrieve a priceless ancient pistol called The Mexican, despite the fact that it means being dumped by his furious girlfriend Samantha, played by Roberts.

When Sam is kidnapped by a hitman who holds her hostage in exchange for the gun, the whole plot spirals out of control.

It was Roberts who threw her Hollywood muscle behind the relatively small budget project first. The script had floated around Hollywood for a while and one stage Bridget Jones star, Renee Zellweger was linked to it.

Roberts only became aware of the project when Brad Pitt's manager sent the script to her agent. Director Gore Verbinski (Mousehunt) took the 35 million dollar project to DreamWorks and discovered her interest.

Having such a major name on board drew in Pitt and DreamWorks cut a deal with both of them to make it for much smaller fees than their usual 15 million dollar a project.

There were also other considerations, like the isolated Mexican location. "I warned Julia that I planned to shoot in Real De Catorce, a tiny town in the middle of the Mexican desert," recalls Verbinski. "There wasn't going to be any proper star motor homes."

What the sought-after actress loved was the script - and she was prepared to forgo the usual Hollywood trappings. "I didn't want to penalize them because they only had so much money for this project.

"I loved the story, there's so much more than simply a romantic comedy. As the movie starts it's the hardest day of Sam's life, she thinks she's finally finished with him (Jerry). But they end up being linked by destiny."

Inside, she insists, she's just the same person, even with all the trappings of Hollywood stardom. "I don't believe there's been any dramatic change in me. What changes with fame is the perceptions of the individual, rather than the individual."