UK atomic war attack predictions and civil defence plans

The whole theory
Operation Square Leg was a 1980 British government home defence Command Post, MoD command and in field exercise which tested the Transition to War and Home Defence roles of the MoD and Government and a mock nuclear attack on the British Isles which assumed that 131 500Kt to 3Mt nuclear weapons would fall on Britain with a total yield of ~205 megatons with 69 ground bursts and 62 air burst occurring.