TOM Uren is 91 now, but he retains a vivid memory of the sky turning crimson when the ''Fat Man'' atomic bomb exploded over the Japanese city of Nagasaki on August 9, 1945.
''I've seen the most beautiful sunsets in the Northern Territory, but this was a magnification of one of those sunsets by about 20 times,'' he says.
Mr Uren had no idea that he was witnessing the second use of an atomic bomb in world warfare, or that it killed 39,000 people instantly and wounded another 25,000, with many more to perish of blast burns and radiation exposure.
He and his fellow prisoners of war were simply overjoyed that, in the days after the sky turned crimson, the Japanese surrendered and they were rescued from enslavement.
''We didn't care how the war ended - we were just happy it was over,'' Mr Uren says. He had spent three years as a prisoner of the Japanese, forced to work on the Burma-Thai death railway before being shipped to Japan to labour in copper and lead smelters. He was in a camp at Omura, about 60 kilometres from Nagasaki, when the sky discoloured.
But Mr Uren, who went on to become a Labor MP for 32 years and served as a minister in the Whitlam and Hawke governments, also became one of Australia's most passionate anti-nuclear and peace activists.
''As I got to understand nuclear war and the nuclear industry I realised the dropping of those bombs on Japan was a crime against humanity,'' he says. ''My old POW mates wouldn't agree with me, of course.''
All these years later, he will bring his anti-nuclear message to Melbourne tomorrow when he launches Hiroshima, assembled by the Hiroshima-Nagasaki Atomic Bomb Exhibition Abroad.
The exhibition of artefacts, photographs and documentaries from the bombed cities will be on display at the Gasworks Arts Park in Albert Park for three weeks before going to Adelaide.
It is being set up by the International Campaign to Abolish Nuclear Weapons, and Mr Uren hopes it will remind those who attend of the danger he believes the nuclear industry poses.
''I'm not a dogmatist,'' he says, ''but every nuclear power station on the planet is an agent of death, threatening to contaminate all around.''
Mr Uren says he did not give a thought to nuclear power until 1959 when he attended the Australian and New Zealand International Congress for Peace and Disarmament - the first such event staged by the left in Australia.
Mr Uren and Labor colleague Jim Cairns became Australia's highest-profile peace activists in the 1960s, leading demonstrations against the Vietnam War, conscription and the nuclear industry. The cause of peace became lifelong commitments for the pair. They were variously revered and excoriated.
Mr Uren laughs about being declared a National Living Treasure by the National Trust in 1997. ''The people who were voting for me would have had me hung in the 1960s,'' he says.
But the old man says he couldn't refuse the invitation to travel from Sydney to Melbourne to launch the exhibition.
''You don't turn down people if they need you,'' he says. ''Giving is loving, you know.''
The exhibition will be launched at 6.30pm tomorrow.