“This is the Wartime Broad­cast­ing Ser­vice. This coun­try has been attacked with nuclear weapons. Com­mu­ni­ca­tions have been severe­ly dis­rupt­ed, and the num­ber of casu­al­ties and the extent of the dam­age are not yet known. We shall bring you fur­ther infor­ma­tion as soon as pos­si­ble. Mean­while, stay tuned to this wave­length, stay calm and stay in your homes.”

These are the words peo­ple would have heard on their radios in Britain fol­low­ing a nuclear attack – that is if they were still alive. The chill­ing script of this broad­cast, writ­ten in the 1970s, has just been released by the Nation­al Archives.

In 1955 the British gov­ern­ment asked a top civ­il ser­vant to assess the scale of the threat posed by a nuclear attack. The Strath Report, as it is known, was declas­si­fied in 2002. It makes grim read­ing.

Strath esti­mat­ed that a “suc­cess­ful night attack” on Britain’s major cities with ten hydro­gen bombs would kill at least twelve mil­lion peo­ple and seri­ous­ly injure four mil­lion more – a third of Britain’s pop­u­la­tion. Such an attack was equiv­a­lent to drop­ping 100 mil­lion tons of high explo­sive. This was, he said, “45 times as great as the total ton­nage of bombs deliv­ered by the Allies over Ger­many, Italy, and occu­pied France through­out the whole of the last war”.

Strath spelled out to his polit­i­cal mas­ters in dry and mat­ter-of-fact lan­guage the utter hor­ror that every per­son in the land might have to face. “Hydro­gen bomb war would be total war in a sense not hith­er­to con­ceived. The entire nation would be in the front line.”

In many of the bombed areas, there would be a total break­down of civ­il order. Chaos would reign. “The house­hold would become the unit of sur­vival,” said Strath. But even those shel­ter­ing in their homes would be at risk from radi­a­tion and fall­out. Up to 50 miles from an explo­sion, peo­ple would receive such heavy dos­es of radi­a­tion that, if they sur­vived, they would be ill for weeks. For a thou­sand square miles around each bomb it would be “sui­ci­dal” even to ven­ture out­side.

“Morale,” con­clud­ed William Strath with breath­tak­ing under­state­ment, “would be very low.”

In this BBC state­ment that has just been released the mes­sage is clear: “stay calm and stay in your homes”. Or, as Lance Cor­po­ral Jack Jones might have said in Dad’s Army, “Don’t pan­ic!” Stay indoors, switch off your gas, don’t use water for flush­ing the toi­let, and ration your food, “because it may have to last for 14 days or more.”

There is though one sen­tence that seems to hint at the appalling scale of the dis­as­ter that has befall­en the coun­try and the world: “Remem­ber there is noth­ing to be gained by try­ing to get away.” Indeed. Quite apart from the invis­i­ble fall­out blow­ing on the wind, where would you go?

You can down­load the full text of the state­ment on the BBC web­site.

“Stay tuned to this wave­length, but switch your radios off now to save your bat­ter­ies until we come on the air again. That is the end of this broad­cast.”