Kiefer Sutherland said American audiences would see a depiction of the capital which was "more true to London" in the latest outing for Jack Bauer.
Speaking at a special screening of 24: Live Another Day in the city, where the mini-series was shot, Kiefer said: "I'm not running by Big Ben, I'm not taking cover in Westminster Abbey, they're going to see a kind of London that's more true to London."
24: Live Another Day is 12 episodes that take place four years on from series eight with Jack living as a fugitive in London, rather than the usual setting of Los Angeles.
Kiefer played the counter terrorism agent for eight series and a film before 2010 and admitted it was hard to get back into character after the long break.
"I think I was quite nervous going into it, just because we took three years off and we were all very proud of the eight seasons we'd done, so opening this can of worms up again, why on earth did we do it? I think that had occupied my mind for quite a while.
"So it took a few days. Jon Cassar, our director, I think I must have annoyed the life out of him because every 10 minutes I was going, 'Is that right, is that who Jack Bauer is?'
"After a few days there was a dynamic shift in energy where his voice gets louder and that I felt very comfortable with and from that moment everything went really well."
He said being older also meant training hard to get Bauer's level of fitness back.
"I'm older, so I was lucky to have four months to really focus on that," the 47-year-old actor said.
"Every season of 24 it's never a question of whether you're going to get injured, it's when and how badly. I find that if you're in reasonable shape, the 'how badly' gets modified and this season was no different. I took a bunch of stitches in the first week, so I like to be in as good shape as I can."
Kiefer added: "Over the course of the eight years I've fractured my kneecap, I've broken my foot, I've broken my toes, I've broken every finger, I've broken ribs... [This series] just cuts so far."
Also on the red carpet at the screening at Old Billingsgate were returning cast members Mary Lynn Rajskub and Kim Raver, and new cast including Tate Donovan, Benjamin Bratt, Gbenga Akinnagbe, Yvonne Strahovski and John Boyega.
24: Live Another Day is on Sky1 on May 7.