Hayley Atwell admitted the stunt work on 'Mission: Impossible - Dead Reckoning Part 1' "blew [her] mind".
The 41-year-old portrays Grace in the film and she had to train "for months" to get in shape, not just for the action sequences but also to keep up with co-star Tom Cruise, who reprises his role as Ethan Hunt.
She told the Daily Star Sunday newspaper: "It blew my mind. Every day on set was like, 'What am I doing today? What am I jumping off?'
"I trained for months with an Olympic martial arts expert to develop a fight sequence for my character that was tailored to my own strengths.
"Then there was the running. I was warned that when Tom Cruise runs, he runs with every cell of his being.
"And it was true. I have never seen anything like it.
"I had to train to have some chance of keeping up with him."
While Hayley learned a lot of new skills for the film, she joked she doesn't think she'll get chance to use them in the real world.
She laughed: "I can also now back-flip over a bridge, jump backwards off a moving train and run uphill in high heels while being handcuffed to Tom Cruise but I'm not sure when those skills might be useful."
Despite the difficulty of making the film, Hayley still had a great time.
She said: "I do enjoy it when I'm able to do [stunts].
"I played rugby at school, so I'm used to being knocked down, brushing myself off and going for it again."
The British star particularly enjoyed one driving scene where she was shackled to her co-star.
She said: "It was intense. We were speeding round Rome with Tom driving with one hand and the other cuffed to me.
"It took months of training for that scene in a little car.
"We got to speed and drift around streets, fountains, down stairs all over Rome. It was quite something."
