Truth-seeking pair have the X factor

David Duchovny and Gillian Anderson star as Fox Mulder and Dana Scully in The X-Files: I Want to Believe, released in cinemas this week. Here they discuss what it meant to return as the iconic characters after six years, the challenges they faced keeping the script top secret, and why the truth might still be out there.

Is the truth still out there? After six years away from the world of the paranormal, alien invasions and spooky phenomena it seems that now, the answer is a resounding yes, with FBI agents Mulder and Scully back in business with a brand new X-Files movie.

But according to David Duchovny, who returns as Fox Mulder, it feels like they've never really been away.

"I never thought about it ending," he says. "We always had the desire to grow the TV show into a movie franchise. We didn't really want it to end.

"We loved the show, we loved the characters, and we enjoyed working with one another. We owe so much to the characters, to each other and to the fans of the show, and we wanted to keep on doing that."

Gillian Anderson, who returns as Dana Scully, and who is currently six months pregnant with her third child, agreed to do the film without so much as a glance at the finished script.

She admits of the film which was co-written and directed by X-Files creator Chris Carter: "My decision to be on board was made a long time before the script was even written. I don't know what I would have done if the script was bad, but fortunately I didn't have to face that.

"We'd had the discussion early on, that were it ever to come to fruition, we'd all be on board for another film.

"With six years having passed when we'd been doing other things both professionally and personally, it felt like good timing."

Hugely successful, The X-Files spawned a movie and ran for nine TV seasons, with viewers in more than 60 countries glued to Mulder and Scully's investigations into unsolved cases involving paranormal phenomena. But shooting the series for 10 months a year took its toll on Mr Duchovny, who left after eight seasons in 2002.

He admits: "I had to leave because of the time commitment. It was never, 'God, I hate the show! I can't stand working with these people!'

"It was always just a case of, 'Let's stop the TV show now because we're all tired, and we've all worked longer than anybody's ever worked on a drama together'.

"You could say there were dramas that went on longer, but not a two-person drama with the same two people. We never changed. We did eight years of the same thing.

"It was really hard for me towards the end of the series run because I didn't really want to be there. I was miserable."

However, Mr Duchovny was keen to step back into Mulder's shoes for the film - a thriller - which is set in real time with both agents having left the FBI. Scully - now working as a doctor - and Mulder are living together.

But their relationship is tested when FBI agent Dakota Whitney (Amanda Peet) asks Mulder to help investigate the disappearance of a female agent, with the help of psychic and convicted paedophile, Fr Joseph (Billy Connelly).

Ms Anderson says: "There are plenty of thrillers throughout history, but what makes the film unique is the particular kind of relationship, the intense relationship, between the two characters.

"It's almost a marriage in a sense. Even though we're not working side by side throughout the whole film, there's that intensity between the characters and the thriller storyline at the same time."

The film also sees the resumption of the powerful on-screen chemistry between Mr Duchovny and Ms Anderson. Despite the actors having rarely been in contact with each other in recent years, they both admit they were able to recreate their characters' special relationship without too much effort.

"The chemistry between David and I is something that is there naturally," Ms Anderson explains. "It has been there despite ourselves, no matter what moods we're in or what was going on in our personal lives.

"No matter how we felt on a particular day - when we were in a scene together, the chemistry was there. There are shades of it in other projects I've done. But there's something different with David and that's the unexplainable bit."

Mr Duchovny adds: "Because we had so little contact there was an element of missing one another and missing working together, that was at play early on in the shooting.

"We had to trust that whatever used to work would continue to work. It's my feeling that we acted as a couple on the television show in all but physical intimacy. We bickered like a couple, we needed each other like a couple.

"I think it's quite similar to actually being a couple. It's hard to work on chemistry. It's either there or it isn't. It's like trying to fall in love with somebody. You can try, but if it's not there, it's not there."

Since The X-Files ended, both Mr Duchovny and Ms Anderson have distanced themselves from Mulder and Scully with a variety of different projects. Ms Anderson impressed in Dickensian BBC drama Bleak House while Mr Duchovny returned to TV in cult US-hit Californication.

Mr Duchovny says of his return to TV: "When I left The X-Files, TV was all consuming and it felt like a box. But six years later, I've done a bunch of other stuff that I've enjoyed, and proved to myself as much as anybody else that I can do other things, so it's not really an issue anymore.

"If you were to ask me, 'Would you go back to doing the television show for X-Files?' I would say no, because the time commitment was crazy. But now I get to do a 12-week season, so it's the best of both worlds for me."

The past 10 years has also seen Mr Duchovny become a parent for the first time - he has two children with his actress wife Tea Leoni - Madelaine, nine, and Kyd, seven. Expectant mum Ms Anderson has one daughter Piper, 13, from her first marriage and a 20-month-old son Oscar with partner Mark Griffiths.

"Having children changes your life tremendously, and in ways that, no matter what anybody speaks about, you never know until you're in the midst of it yourself," says Ms Anderson, who lives in London.

"I've got friends who are completely paralysed by it and friends who behave as if it's just a tiny bump in the road. I think I'm somewhere in the middle."

It seems unlikely that if The X-Files: I Want to Believe does good business at the box office, fans will have to wait another six years to see more of their favourite FBI agents. But will David and Gillian be interested in opening the X-Files again?

"We'll see," says Mr Duchovny.

"It works and it can work forever as long as the stories are good," he adds.