Eddie Redmayne's attempts to hone his spying skills were thwarted by a group of tourists

He told Britain's HELLO! Magazine: "I worked with Paul Biddiss, our brilliant military espionage advisor.

"He taught me all of these techniques, like how to walk down the street and see people in car window reflections and car mirrors.

"I had to walk through Covent Garden in disguise and he would send me photos of people I was meant to track.

"I was tracking this one person, thinking I was doing really well and staying completely undetected, until a group of tourists stopped me and asked for a selfie. That was a little bit embarrassing."

Though Eddie is unsure if he'd make a convincing spy in real life, he did pick up some useful tips.

Asked if he thinks he'd be a good spy, he laughed: "I'm not sure about that.

"I've learned some really handy tips though. One is that if you're being chased, have your hand in your pocket so you can use the butt of your phone as a weapon if you need it. Or use change as some sort of shrapnel to throw in your attacker's face.

"The other thing I learned was how some soldiers carry tampons to stem the bleeding if they are shot."

The series saw the Oscar-winning actor spend hours getting into character as prosthetics experts crafted his various disguises.

He said: "It was a lot of time spent in make-up, working with the most brilliant prosthetic artists.

"The prosthetics take about four hours to put on and two hours to take off, so it was a lot.

"Seeing the process he goes through to stay undetected and then having that moment when he peels off the mask for the big reveal is something I really love about the role."