It was a warm spring morning, April 26, 1986, when the world's worst nuclear disaster occurred at Chernobyl in the former USSR (now Ukraine).
After the disaster, the workers' town of Pripyat was emptied - its inhabitants never to return to their homes.
Millions of people were subjected to radioactive fallout.
But was it quite the overwhelming tragedy that most reports have suggested?
Bridget Kendall travels to Chernobyl to find out, with contributions from former residents and experts - including Dr Hans Blix, then Director of the International Atomic and Energy Authority.