Government files released today reveal how Northern Ireland was expected to cope if it was targeted by a nuclear bomb.
In the early 1980s, with the world still polarised by Cold War tensions, officials were privately drawing up detailed plans for coping with a doomsday attack.
A huge file outlines in terrifying detail what would happen during the countdown to a nuclear apocalypse - and beyond.
Yet despite the extraordinary plans, the documents also describe how people should be encouraged to stay calm in the run-up to a nuclear attack.
One document states: "The general aim in the crisis period preceding a nuclear attack would be to keep disruption of the social, economic and industrial life of the country to an absolute minimum."
It describes how national announcements would advise the public to carry on with their day-to-day activities.
The revised plans for a nuclear attack, contained in files released today by the Public Record Office, were drawn up in 1981.
It was a turbulent time in world politics. The Reagan Presidency was under way in the US, warming up Cold War hostilities between east and west.
Officials planning for a nuclear attack on Ulster believed Belfast was the most likely target.
It reported that a three megaton bomb - equivalent to three million tons of TNT or 150 times more powerful than the Hiroshima bomb - was "considered a likely-sized weapon".
One map suggests the range of impact from a nuclear bomb dropped on Belfast City Hall.
Buildings within a three-mile area would be destroyed and streets left impassable, while houses in a further three-mile band would be left irreparably damaged.
It notes that surrounding towns including Bangor, Donaghadee, Castlereagh and Downpatrick would all be "severely affected" by the fallout.
Another document details how, in the event of a nuclear attack, central Government would cease.
"On the current planning assumptions if an attack took place in Belfast the major Government offices in the Stormont estate and the city centre would be destroyed either by blast or fire," it continues.
A Northern Ireland Central Control would provide the highest level of Government, while a regional commissioner - expected to be the Secretary of State - would have the power to regulate all goods and services.
The papers warn how special powers would be enacted.
"These would include powers authorising ministers to control industry, requisition land and buildings and acquire articles of all descriptions," one adds.
Other show BBC plans to maintain local radio stations.
Anyone concerned about a surprise atomic attack need not have worried unduly.
Information about nuclear bursts and resulting fallout was obtained through a network of underground monitoring posts and assessed at the UK's Warning and Monitoring Organisation in Lisburn.
The sophisticated electronic systems would provide "a minimum of a few minutes' warning", one briefing paper noted.