Max Pearson presents a collection of the week's Witness History interviews from the BBC World Service. It’s 50 years since soldiers of the communist Khmer Rouge party stormed into the capital, Phnom Penh. It was the start of a four year reign of terror which resulted in up to two million people being killed. We hear two stories from people affected by the regime. Our guest is journalist and author, Elizabeth Becker. She is one of the foremost authorities on the history of Cambodia, and one of the few westerners to have interviewed Pol Pot.The scientist who invented the white LED lightbulb in 1993 tells his story.Plus, the Bali Nine: young Australians facing the death penalty for drug smuggling and, Spain’s historic link to World Book Day.Contributors:Youk Chang – lived through the Khmer Rouge regime Aki Ra - child soldier of Cambodia Elizabeth Becker – journalist and author Professor Shuji Nakamura – inventor of the white LED lightbulb Bishop Tim Harris – friend of one of the Bali Nine families Pere Vicens - book publisher and one of the creators of World Book Day(Photo: The fall of Phnom Penh in 1975. Credit: Roland Neveu/LightRocket via Getty Images)

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