"But my character is certainly the most emotionally unstable. She’s always had to be quite self-sufficient. Her mum has had her very young, so her mum has certainly had her own life. And Shannon has never wanted to feel too much of a burden to her mum.

"She wanted to get as much emotional contact from her as possible - to piss her off basically! So she keeps herself to herself."

For his fourth girl, the rebellious and streetwise Kerrys, Clarke turned to another old friend and collaborator, Shanika Warren-Markland, who played Kayla in Adulthood. Admitting that she immediately 'loved' the character when Clarke sent her the script, the actress believes that Kerrys is very different from her Adulthood role.

"Kerrys knows her own mind. And she likes her trainers. She likes her little short skirts and sports tops. This is what she likes to wear. I don’t think Kayla would’ve been like that - she was a bit more serious."

The bulk of Kerrys’ story revolves around her clashes with her half-brother Manuel (played by Gregg Chillin). "She has a lot of issues with her family that I think at first she’s not admitting to herself. That leads to a lot of things that she does, because of the family issues that she’s got going on.

"And they’re confronted throughout the few days of the film, I think that does change her. You do see a difference. Not a resolution exactly but a new beginning, with the family situation.

"It’s discussed, the issues with her family, and then she comes to an agreement with herself, so you see that journey as well."

Clarke and Davis took great pains to ensure that some strong supporting players surrounded their four stars. Sean Pertwee was cast as Shannon’s father and Helen McCrory was brought in to play Joanne’s mother.

Bionic Woman star Michelle Ryan was later cast as Kelly, the ruthless dealer who will stop at nothing to get the diamonds, while recording sensation Eve was hired to play Latisha, a tough New Yorker that helps Cassandra out of a tight spot.

Perhaps the most unusual coup was the securing filmmaker Kevin Smith to play Big Larry, a foul-mouthed courier Cassandra meets on her way to New York.

An avowed Smith fan, right back to his debut film Clerks, Clarke eventually met his hero at ComiCon, the San Diego-based annual convention from fans of sci-fi and fantasy films, comics and television shows. After expressing his admiration for the director, they kept in touch.

"When this came up, I realised he was coming to London around the time we were filming to do his book tour. So I said, ‘Since you’re here anyway, do you want to appear in the film?’

"I sent him an e-mail. He said, ‘Let me read it.’ And he read it and said ‘Yeah. Providing I’m not topless or bottomless, I’ll do it.’"

No stranger to acting, having appeared as Silent Bob in a number of his own films, Smith didn’t need much direction, according to Davis. "He actually asked, ‘Do you mind if I add a few lines?’ And this was Kevin Smith! What the hell is he talking about? Of course he can!

"He was so good to work with. He really wasn’t an ego or anything. He was just really open and himself, and had this energy and a way of doing stuff, which felt semi-improvised. He just gave that extra thing which is what you hope from any good actor."

So was there any chance of Davis getting a cameo in the next Kevin Smith movie? "I plan on staying entirely behind the camera," he smiles. "But I’m certain Noel should."

Finally, Clarke cast himself as Tee, the aggressive middle-man in the diamond robbery who is working undercover at the 24 Hour mini-mart where Joanne has been forced to cover for her father.

"He’s kind of a manipulative little trouble-maker really," Clarke says, with a grin. He points out he doesn’t mind playing in a supporting role. "The film was really about the girls, so that wasn’t a problem. My main thing is that people don’t think I write my films to benefit me.

I just like writing scripts. It’s not about me starring as the hero on the hill with the wind blowing through my hair."

4.3.2.1. is released 4th June

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