The speech, devised by senior Whitehall officials to announce Britain's involvement in what was feared as the Third World War, was never recorded.
"Not for a single moment did I imagine that this solemn and awful duty would one day fall to me," reads the imaginary broadcast, released here today as part of Britain's 30-year de-classification rule for classified documents.
"But whatever terrors lie in wait for us all, the qualities that have helped to keep our freedom intact twice already during this sad century will once more be our strength," the speech said.
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Blue forces - representing NATO - retaliate with a "limited-yield" nuclear strike, forcing Orange to initiate a peace process.
The exercise came in the year that US President Ronald Reagan denounced the Soviet Union as the "evil empire" and deployed US nuclear cruise missiles to Europe.
Striking a personal note, the Queen's imaginary speech went on: "My husband and I share with families up and down the land the fear we feel for sons and daughters, husbands and brothers who have left our side to serve their country. My beloved son Andrew is at this moment in action with his unit and we pray continually for his safety and for the safety of all servicemen and women at home and overseas."
The Soviet Union and the US later negotiated a reduction in the number of nuclear weapons, as the Cold War came to an end and averted the risk of another, potentially apocalyptic World War.