Relatives of British POWs who had been on the ship attend the screening of a documentary about its sinking in London on Tuesday. CHINA DAILY

As the documentary The Sinking of Lisbon Maru ended in the British Film Institute's Southbank theater, in London, England on Tuesday, long-lasting applause erupted, and tears welled up in the eyes of many in the audience.

The Lisbon Maru was an armed Japanese cargo ship that participated in World War II, and the documentary told the lesser-known story of hardship, horror, tragedy, and courage that surrounded its sinking while transporting more than 1,800 British prisoners of war, or POWs, from Hong Kong toward Japan.

The sinking by a US submarine happened because the vessel did not bear a sign indicating it was carrying POWs, who were battened down below deck at the time and who were left to drown by the Japanese soldiers on the ship.

When the Lisbon Maru went down off the coast of East China's Zhejiang province on Oct 2, 1942, local Chinese fishermen sprang into action, pulling 384 POWs from the water.

Another 800 went down with the ship.

Tuesday's special screening about the tragedy featured a film in the final stages of production, and was organized for around 400 descendants, relatives, and friends of the POWs who had been on board.

Many of those in attendance had previously been interviewed by the filmmakers. Most were seniors, but there were also some with young children, and even a few who flew in from Australia.

Mark Weedon, the 83-year-old son of Martin Weedon, who had served with the Middlesex Regiment and who survived the incident and lived until age 60, said: "I'm here to honor those who didn't make it, as well as my father and my godfather, who did make it… and I hope people remember them."

Fang Li, who produced the documentary, said: "It's an untold history. We see the bravery of our Chinese fishermen. We hear heart-breaking stories of individual British families, one after another. And we are angered by Japan's attempt to cover up the brutal crime."

Wearing a T-shirt with the coordinates 122°45'31.14" E, 30°13'44.42" N, which are those of the sunken Lisbon Maru, Fang said he first heard about the incident from a ferry captain in the Zhoushan archipelago, Zhejiang province, while shooting another film in 2013.

Moved by the story, Fang surveyed the area in 2016 and, with sonar detectors mounted on drones, located the wreck.

In the following years, he and his team contacted more than 380 relatives of the POWs and interviewed 120 of them, including the only two British survivors still alive at the time.

"While I was doing this, I was totally touched by those young boys, the age of my son. So many of them lost their lives there," he told the BBC in 2018 after posting adverts in British newspapers seeking descendants of the POWs.

At the end of the screening, Fang told those in attendance: "Today is a very important moment for all of us. Because of this film, we are all bound together for the history, for the memory of our children."

The film's history consultant, Tony Banham, a British historian based in Hong Kong, was among early researchers into the incident and wrote a book, The sinking of the Lisbon Maru: Britain's forgotten wartime tragedy, in 2006.

Banham said after the screening he could hear people sobbing from the moment the film started.

"The true story of war is grief," he said. "It's the impact on families. So many documentaries about war talk about the glamor of war, the aircraft, the tanks, the colorful explosions. But the real long-term impact of war is on the families of those who were killed and those who survive."

Zheng Zeguang, China's ambassador to the UK, said at the screening: "This documentary has brought to life the cruelty of war, the atrocities of aggressors, and the righteous and heroic act of rescue of those Zhoushan fishermen.

"One important inspiration we may draw from the Lisbon Maru incident is that peace does not come by easily, and lives are the most precious. Today, against a complicated world which is far from being tranquil, let us remember that historical event, commit ourselves to increasing understanding, collaboration, and friendship and make joint efforts toward world peace."

The film featured an interview with Lin A'gen, the last survivor among the Chinese fishermen, and a 2019 visit by descendants of the POWs to Zhoushan, where they met him. Nicola Brooks, granddaughter of one of the POWs, said: "Despite the sadness, the upset, and the brutality, what I felt from the film was the fact that the Chinese fishermen helped the British prisoners of war. That unity will prevail. It will just shine through. And I'll take that away with me."