Jeremy Irvine underwent terrifying waterboarding sessions to get into character for his new film The Railway Man.

The star plays Scottish soldier Eric Lomax, who was captured and subjected to extreme violence in Thailand during World War Ii, and to fully understand what he went through, Irvine told director Jonathan Teplitzky to push him to his limits.

The War Horse actor tells Britain's Daily Mail, "I said: 'Go for it, Ok? No stand-ins, no faking.' We rehearsed how we were going to do it, and I was controlling it all the way through.

"It was b**ody unpleasant, but I knew I wasn't in any danger. But I felt it was important that I convey the hell Eric went through.

"It had to look as real as possible. The older Eric is played by Colin (Firth) and to make sense of the trauma Eric experienced later, it was vital that he be seen to suffer through this awful torture.

"I was waterboarded for seconds at a time, over the course of two days, while the real Eric Lomax had to endure the real thing, time after time."

The form of torture involves a cloth being place over the mouth and nose while water is poured over, giving the victim the sensation of drowning.