April 26 1986, operators at the Chernobyl plant, thought to be one of the best run in the former USSR, made a mistake when carrying out a test on one of its reactors. Attempting to correct it, they deliberately overrode a series of safety systems designed to prevent an accident. After the last was switched off, the reactor's power surged several hundredfold in a second. Two huge explosions blasted the 1000 metric tone lid clean off the reactor and lit a fire that blazed for 10 days, releasing several quadrillions of becquerels of radioactive isotopes.

      As a result of fallout from the accident, 31 people died and 135 000 had to be permanently evacuated. Between 20 000 and 40 000 people will die of cancer in the USSR and Europe over the next 30 to 60 years from increased radioactive doses. Many more would have died if it had not had happened at night, when people were indoors and less exposed to radioactivity, or if the weather conditions had brought the fallout down only locally. But the winds ensured that radioactivity spread more widely. All of Europe from Iceland to Greece was affected. Restrictions on foodstuffs were imposed in almost every Western European country and imports from Eastern Europe were banned. Four years after the accident, hundreds of sheep farms in Cumbria and Wales were still so radioactive that they could not sell meat for consumption from sheep that grazed on the pastures, and the Lapps of Scandinavia faced the destruction of their culture because their reindeer were contaminated by eating lichen which accumulate radioactive material.