24: Live Another Day – Kiefer Sutherland on the return of Jack Bauer

Four years ago, I was lucky enough to attend the premiere of the opening episode of the eighth series of 24 in New York. As the house lights came up, the audience began chanting: "We want more! We want more!" Well, now their wish has been granted. As the posters all over the country have been reminding us: Jack's back.

The un-killable Counter Terrorist Unit agent Jack Bauer, who in the interim has remained hugely popular with DVD "binge-watchers", returns after a four-year hiatus to try to foil another terrorist plot that threatens to bring about the end of Western civilisation as we know it.

Kiefer Sutherland, the star of 24, confesses that after agreeing to reprise his most celebrated role, "For the next six months I was absolutely terrified about why I'd opened this can of worms once more. But once we got on set, within two or three days, I felt right at home again."

24's groundbreaking storytelling technique – the show pioneered the "real time" format with a ticking clock constantly onscreen – makes this the most viscerally exciting, nay addictive show on TV. With its outlandish plots, outrageous cliffhangers and brilliant twists (its motto may as well be, "trust no one, especially the person you think you can trust the most"), the show has hooked fans all over the globe. One well-known aficionado, President George W Bush, once told regular 24 cast member Carlos Bernard that, "All I can do is watch that show of yours."

I meet Sutherland on the set of the ninth season, 24: Live Another Day, which starts tomorrow on Sky1 HD. It is being shot in a suitably distressed, derelict factory in west London. Sutherland, who was born in London, sums up the plot of 24: Live Another Day thus: "Jack will have a crappy day and be tested in a thousand different ways!"

Since the end of the last series in 2010, Jack has been lying low in Eastern Europe. But he resurfaces in London when he hears of a terrorist plan to wreak havoc. Yet again, he has just 24 hours to save the world.

He teams up with his long-time cohort, geeky computer genius and firm fan favourite, Chloe O'Brian (42-year-old Mary Lynn Rajskub).

The show has always attracted obsessive fans. Some of the more out-there aficionados enjoy playing the 24 drinking game, in which they have to neck an alcoholic beverage every time Jack says his celebrated catchphrase, "Dammit, Chloe!"

Sutherland is far more good-humoured than his famously tight-lipped alter ego – Jack is a man who has not knowingly cracked a smile in the past 13 years. The actor owns up that in the past he has mischievously ad-libbed the catchphrase many times per episode – with predictably messy results in sitting rooms around the world.

But for all the super fans' over-the-top behaviour, Sutherland embraces their fixation with the show. The star, who is sitting across the table from me in the sort of anonymous interview room in which Jack has conducted some of his more, er, "vigorous" interrogations, says that, "In the past when fans in the street would call out to me, 'Jack!', I didn't respond.

"But now I'm proud of it. I've spent a third of my professional life doing this show, and I love the fact that people adore it. Nobody puts on a play and doesn't care if just three people show up. This show is making up for the times in my life that that's happened to me!"

The actor, who is ridiculously fit and looks much younger than his 47 years, goes on to assess what state Jack is in at the beginning of 24: Live Another Day. "I was telling a friend the other day that this time Jack is going to be meaner than he's ever been before. My friend asked, 'Is that possible?' Oh yeah, it is!

"The reason is that is by the end of season eight, the CIA want to eradicate him, he is estranged from his daughter, he will never see his granddaughter again, he has lost his great love Renee Walker, and is on the run from the country he spent his life serving. He's spent the last four years hiding out in Eastern Europe – all of those things would piss me off!"

But as the season unfolds, "He progresses from that very hard place. Water slowly starts to trickle out of little fissures in the rock. I think it's very interesting to watch someone's difficulty as they have to confront the reality of who they are."

The character of Jack has over the years stirred up some controversy – his excessive use of torture, for instance, triggered a lot of criticism. But for all that, he remains a widely loved character.

So just why, despite everything, is Jack so enduringly popular? Perhaps it is because we can all identify with his fallibility in the face of impossibly tough decisions. Sutherland explains that the almost insoluble ethical dilemmas Jack confronts on an hourly basis are, "the root of the show. When I was 11, I did a play in Los Angeles called Throne of Straw.

"The play was set in the Lodz Ghetto during the Second World War. It was about an elderly Jewish man in charge of selecting people to be sent from Lodz to Auschwitz. He thought that if he could protect the children for bit longer, then the Nazis might not eradicate every Jew. Even at the age of 11, I had unbelievable empathy for that character. I feel the same for Jack."

Sutherland continues that, "Jack is forced to make these impossible decisions – to save 1,000 people, are these 10 people an acceptable loss? You can't win. We all feel that. We think, 'I've got a promotion and a raise. It will mean I see less of the kids, but I can put them through private school.' No one wins cleanly.

"Our lives are complicated. Jack's experiences are ridiculously out of proportion, but one of his most relatable qualities is that nothing in his life is ever clean. I think people relate to that."

So where next for Jack Bauer? Could he be smuggled into Eastern Europe to try to sort out the unrest in Ukraine? "There you go!" exclaims Rajskub. "24 has always mirrored reality. You've got the next series right there!"

'24: Live Another Day' starts on Wednesday at 9pm on Sky1 HD