Meeting the man who, under torture, revealed information that led to the capture of his grandfather by the Japanese during World War II was an emotional experience for Perth's Luke Thomas.
It happens during the SBS documentary series Australia's Secret Heroes. The secret heroes were members of the Z Special Unit, plucked from the Australian military and sent on perilous undercover operations in Asia.
Thomas, 27, is one of six descendants of the heroes featured in the three-part WA-produced series who are sent on training missions to appreciate what their forefathers went through.
Before the series Thomas had scant knowledge of his grandfather, Jack Cashman, a communications officer who spent 18 months in East Timor as a POW and died in his late 60s.
"I had written an assignment on him in school with the help of my mum and I heard a few stories but that was about it," he says. "I never met him, which I regret."
Thomas learnt how, upon arrival in East Timor, his grandfather had been ambushed by the Japanese. "He was set up and doomed to failure, so that was difficult to take on board."
In the toughest moment of filming, Thomas meets the veteran, Jim Elwood, whose torture led to his grandfather's ambush.
"Jim is in his 90s now and for the last 70 years has been living with these feelings of guilt and regret.
"Until now he has never spoken about it. I think it helped him to meet the grandson of one of the men involved. He left with a bit of a smile on his face.
"We were exposed to some of the torture techniques they would have been put through and anyone would have caved.
"These guys were just teenagers expected to do extraordinary things."
Thomas says he wasn't expecting the series, which also uses interviews with veterans and historical footage to give an insight into the unit's daring exploits, to be such an emotional journey.
"It had been pretty much pitched to us as a sort of commando school but it was more of an emotional experience.
"Every day we learnt more about our ancestors in a way that helped us feel empathy for them and put us in their shoes.
"A lot of information was thrown at us. One of the main messages I got was our ancestors weren't highly skilled operatives but teenagers who were just given a few months of training."
Two of the other relatives featured are also from WA. They are Brenden Sue, grandson of Blood On Borneo author Jack Wong Sue, and Tian Williams, grandson of Teh Soen Hin, nicknamed Tommy Teh the Headhunter.
Thomas said the six descendants formed a strong bond during filming. "Particularly in the evenings when we were stuck in tents and there was nothing much to do but drink lots of tea and talk. I would like to think we will stay in contact but the reality is we all have pretty different lives. Social media will help, though."
Thomas, who is in Perth doing a doctorate in marine biology, was born in Melbourne but grew up in America.
"In the past when I visited Australia from America I felt I didn't entirely fit in. This experience has made me feel a bit welcomer somehow. I feel closer to my family here."
'One of the main messages I got was our ancestors weren't highly skilled operatives but teenagers who were just given a few months of training.' LUKE THOMAS