In fact it's so covered that until the Tory U turn this week, the UK had agreed to reduce the stockpile of warheads to 180 - just enough to destroy all life on earth twice.
The thing is I'm struggling to think of any modern threat scenario in which nukes could be used - 9/11? Iraq War? The Falklands? London Bomber? Novichok dude in Salisbury? We certainly wouldn't want to be going into a mutually-assured destruction scenario with one of the big 3.
So what possible justification is there for Boris to decide that we need more warheads? His mate is an arms broker?
Wouldn't the money be better spent on modern deterrents or saving society?