Are the existence of these letters not a paradox to the theory of Nuclear deterrent? If the purpose of a nuclear deterrent is to mean that the weapons are never needed to be used then we should need the letters to order their use?

It does fascinate me what former PMs would have written. Surely Thatcher would have written 'attack the commies and while you're at it fire a couple at Buenos Aires and north England'

I still think that the best option would be to place the vessel under command of a friendly nation.