During this recent Atlantic Council event, the FT’s Demetri Sevastopulo recounted this anecdote concerning authority to launch British nuclear weapons:
a former British defence secretary asked me during the Trump administration,would it be possible for President Trump to launch a nuclear weapon without anyone stopping him, and how did theprocess work. And I said, there are lots of theories; I don’t know the exact answer. How did it work in the U.K? He said, I don’t know. They never briefed me on what I would have to do.
Almost certainly because the secretary of state for defence isn’t involved ex-officio; the prime minister selects the two nuclear deputies at her own discretion. One of them usually is the defence secretary but this is not a binding condition.
I can well imagine that one or more of the three possible candidates might not have been so selected. (Fallon: lifetime backbencher until promoted direct into the Cabinet to general astonishment, disgraced as a sexual harasser. Williamson: party apparatchik, repeatedly disgraced for various reasons, widely seen as an idiot. Mordaunt: lightweight, very briefly in office.)