Veterans and historians of the Thai-Burma railway tell the story of its construction. Built to supply Japan's invasion of India, it cost thousands of lives - both POWs and Asian slave labourers. Shot on location, the episode describes the building of one of the harshest sections of the line - Hellfire Pass, and seeks to explain cruelty of the Japanese railway engineers. Using a stolen engineer's map, historian Rod Beattie explains how a key section was built. Lt Colonel Huw Parker, a serving Royal engineer, explores the Wampo Viaduct - the largest surviving wooden construction on the railway, and pays tribute to the men who died building it.