Australia held off on ratifying the treaty. But in 1972, the conservative Gorton government was swept from power and replaced. Gough Whitlam, a longtime advocate of arms control, wasted no time ratifying the NPT and abandoning the Jervis Bay reactor. In a heartbeat, the 40-year quest for Australian nuclear capability was over.

There is, however, one startling and little known postscript to Australia’s nuclear weapons journey.

Unlike the U.S. ballistic missile submarine fleet, the British nuclear deterrent has a curious twist in its command and control structure. Welded to the floor of the control room of each British missile submarine is a safe containing a document known as the “Letter of Last Resort.” The role of the letter is to provide orders to the commander of the submarine in the event the United Kingdom had been destroyed by a pre-emptive nuclear strike.

Little is known about the contents of the letters and no British prime minister has ever disclosed the specific orders.

A number of senior public servants have given some insight into the choices presented to each prime minister for the letters. In brief they were:

Try to identify the attackers and retaliate;

Do not use the weapons as causing further destruction would be pointless;

Place yourself under Canadian or Australian command.

The possibilities left open by these options are as intriguing as the letters themselves. As the Cold War continued, its major combatants became capable of destroying each other many times over. Most major powers including the United Kingdom, the United States, the Soviet Union and possibly China would have been smashed after a nuclear exchange.

Similarly, Canada’s close proximity to the United States and the essential role played by it in air defenses would have made it an attractive target.

Australia’s circumstances were somewhat different. Intelligence estimates did forecast that the USSR would attack Australia with nuclear weapons in a global exchange. However, the missiles would most likely target local U.S. facilities, which were in isolated areas of the continent.

Considered together, this scenario leaves us with something befitting of a Greek tragedy. A battered but still coherent Australia, alone and without allies, could have found itself holding the British nuclear card it had sought for so long – only to find there was no one left at the card table.

This piece first appeared in WarIsBoring here.