10 October 1957,
The nuclear accident occurred in the UK, the most serious in the country. One of the two Windscal reactors built to carry out the British atomic bomb project was set on fire for three days by burning plutonium and spreading radioactive air pollution. The British authorities devalued the facts and information about the fire was heavily censored. No one was evacuated, but they ordered not to drink milk from 500 square kilometer cows. An estimated 240 people died from radioactive cancer.
Source:
Wikipedia – Windscale fire.