Dame Helen Mirren stars in a new espionage thriller called The Debt. The inspirational actress talks about reuniting with John Madden, who she worked with on Prime Suspect, geriatric fight scenes and being haunted by those bikini shots.

Dame Helen Mirren is sitting in a chair with head in her hands, giggling. She’s been reminded about her most recent honour where she beat the likes of Elle MacPherson, Cheryl Cole and Jennifer Lopez to be crowned Body Of The Year. “I’m grateful for the kindness of strangers,” says the 66-year-old with a familiar and mischievous glint in her eye.

“The reality is that I’m in a permanent state of guilt for not exercising enough. I’m just like anyone else really, it’s a constant struggle,” says the actress who won an Oscar for her role as Elizabeth II in 2006’s The Queen. She does watch her weight though, she concedes: “You know, to a certain extent, but not obsessively.”

Mirren has never been one to shy away from stripping off. And indeed she’s always been lauded for her physical attributes and barely latent sexuality during her 40-year career. That said, the shot of her posing in a red bikini, looking tanned and toned on an Italian break in 2008, still managed to generate headlines.“That photograph will haunt me for the rest of my life,” she says.

In an interview she said there was a sense of shock that a woman in her sixties could look like that, but today she says: “It’s a lie. I just cover it up well.” She’s doing herself her a disservice, of course, because in the flesh she looks remarkable. She’s promoting her latest film, The Debt, a two-tiered espionage thriller about three retired Mossad agents who have been venerated for decades by Israel because of a secret mission they embarked on in the Sixties.

Mirren stars as the only female agent Rachel Speed, while the up-and-coming actress Jessica Chastain, who recently appeared alongside Brad Pitt in The Tree Of Life, plays her younger incarnation.

“It’s old-fashioned storytelling with a great, great story,” says Mirren. The movie sees her reunite with her former Prime Suspect director John Madden (who won an Oscar for Shakespeare In Love.)Madden only ever had one actress in mind for the role that, he says, would require a woman “to be very strong, but at the same time, vulnerable”. Mirren responded immediately to the challenges.

“Aside from wanting to work with John again, I was interested in exploring how every action you take has a consequence,” says Mirren. Having learned to live with compromise in The Debt, Rachel slowly arrives at the realisation that it doesn’t always work. “She’s not a person who reveals much to anyone, not even to the daughter who has written a book about her,” Mirren explains.

“Rachel has buried her true emotions and existed for many years on a superficial level, not confronting the depth of her true feelings.” This posed particular challenges for Mirren, who says that while she’s never been the kind of actor to take a role home, the part of Rachel required a huge amount of concentration. “Although there’s not a lot of dialogue, there’s this internal story that you have to communicate without words,” says Mirren.

Next up will be period piece The Door and she’s currently shooting a biopic on the Phil Spector story with Al Pacino. “To be on set with one of the greatest living actors and watching him work is really, really thrilling,” she says, breathless as a newcomer.

As inspired and excited by her career as she was 40 years ago, this Dame’s certainly not slowing down any time soon.