Sir Mark Rylance has said a recent trip to Hong Kong to discover the part his grandfather played in the Second World War made him realise there is no “right or wrong” in battle.

The actor and Stop The War Coalition supporter, 59, made the trip during the recording of My Grandparents’ War, a Channel 4 programme marking the 80th anniversary of the conflict.

The Oscar-winner’s grandfather Osmond Skinner, a banker for HSBC, defended the territory as part of the Hong Kong Volunteer Defence Force with little to no training.

The 88th Academy Awards – Vanity Fair Party – Los Angeles
Mark Rylance holds up his award for best supporting actor (PA)

He was shot on Christmas Day and spent almost four years as a Japanese prisoner of war.

Sir Mark said Japanese and British forces had been “fooled by ideas of empire” and that finding out about his grandfather’s treatment had only reinforced his anti-war leanings.

He said: “The trip to Hong Kong convinced me of a rather shocking thing – that (I) don’t really believe in talk of Geneva Conventions and right and wrong behaviour in war, that there are war criminals and not war criminals, any more.

“In the few fights I’ve been involved in – not with heavy weapons or artillery, just fisticuffs and anger and self-righteousness and defensiveness – everyone has been brutalised.

“You can’t say to someone, ‘Oh, you didn’t fight fairly’.

“I think that’s all a con to get young people to sign up, as if it will be a civilised thing they’re going to. I don’t believe it at all.

“I don’t think he would agree with everything I say but I think he would be very interested to talk with me about it.

“I think that he and I would share a faith that there is goodness in people. Os was a very just man, but he had been through something terrible.”

My Grandparents’ War starts on Channel 4 on November 27.