Macmillan 's decision led to increased demands on the Windscale and ( subsequently ) Calder Hall nuclear plants to produce plutonium for military purposes . As a result , safety margins for radioactive materials inside the Windscale reactor were eroded . This contributed to the Windscale fire on the night of 10 October 1957 , which broke out in the plutonium plant of Pile No. 1 , and nuclear contaminants travelled up a chimney where the filters blocked some , but not all , of the contaminated material . The radioactive cloud spread to south-east England and fallout reached mainland Europe . Although scientists had warned of the dangers of such an accident for some time , the government blamed the workers who had put out the fire for ' an error of judgement ' , rather than the political pressure for fast-tracking the megaton bomb
Windscale fire
Windscale fire
Harold Macmillan