According to the reporters for BBC Radio 4, the safe containing the safe containing the Letter of Last Resort is to be opened only in the event of a nuclear attack on Britain that kills both Prime Minister Gordon Brown and a second, not identified person—the person he's designated as his alternate nuclear decision-maker in case of his death.
Assuming the death of his second as well, Brown's letter, the voice from the grave, from a person most probably reduced to radioactive ashes, will (theoretically) condemn to fiery death tens, perhaps hundreds, of millions of innocent civilians.
Here is how the reporters described the writing of the most recent Last Resort Letter in their Daily Mail article:
Within days of coming to power, Gordon Brown had to make a decision with potentially massive consequences for Britain and the world.
Would he, in the event of a surprise nuclear attack in which he was killed before he could react, want Britain's last line of defense—a lone Trident submarine on patrol somewhere under the Atlantic—to retaliate?
Brown wrote his answer to that question four times, in long-hand, in the form of letters addressed to the Royal Navy submarine commanders who, we must all hope, will never be required to read one of them.
We are told that every prime minister in recent years has written such a letter and that letters that go unused (Tony Blair's for instance) are destroyed without being read.
This procedure raises several questions. If Gordon Brown wrote his letter more than a year ago, how would he (or any prime minister) know exactly why and by whom Britain might have been struck?
As the Daily Mail piece puts it:
How on earth does [the submarine commander] know if the PM has been killed and the normal chain of command obliterated? For obvious reasons, no one we spoke to would elaborate on the precise protocols. Suffice it to say that there is a complicated series of checks that the submarine commander must perform to establish the true situation—one of which, curiously, is to determine whether Radio 4 is still broadcasting.
During the Cold War, the origin of a nuclear attack would have been fairly easy to determine: The only nation likely to strike was the U.S.S.R. Now? A single wobbly missile from some Pakistani terror group from a freighter offshore? A series of terror bombs smuggled into the country whose detonation had—as they say in the nuclear terrorist trade—"no return address." Who would the sub captain target if the PM posthumously ordered a retaliatory launch? Would the Last Resort Letter provide any guidance except a Big Yes or a Big No? And it's not clear whether the captain is required to show the letter to anyone else. If the captain's the only one who reads the letter, what's to prevent him from substituting his own decision, his own notions of justice and vengeance, of what's ethical and what's not, for the PM's, from burning the letter and deciding for himself whether or not he wants to kill tens of millions of civilians depending on his mood or what he ate for breakfast or whether he had a fight with his wife before the sub left home?
And what if it's a mistaken launch by a salvo of Russian nuclear missiles that succeeded in vaporizing the United Kingdom? Should millions of citizens of Moscow and St. Petersburg, say, be destroyed without a chance to plead their case that it was a human or mechanical error? How would the sub commander know the circumstances if there's no one in authority left alive (or no functioning communications equipment to let him know)?