Lewis left out "unusable"
"an unstoppable, unfindable nuclear hammer capable of shattering a nation in an afternoon," and sadly unusable because they cause so much wide spread devastation.
I do not believe for one minute that the UK would deploy nuclear weapons against the China, Russia, Pakistan, India or Israel that will exist in 10 years from now in retaliation for anything. Even if they attacked an ally, took our PM hostage during a state visit, or did to our children what employees of Vatican City did to our children, we would not see that as worth the price of a nuclear war.
It is even less likely that we'd use nuclear weapons against a non-state terrorist or pirate group.
I know it. You know it. Our enemies know it. Nuclear deterrence only works when the threat of use is credible, and our little island nation can't credibly make that threat.
It would be as if the UK spent huge amounts of money on biological and chemical warfare weapons in the years between WWI and WWII. A total waste because we are not prepared to actually deploy them under any circumstances.
On the other hand, spending money on nukes when "our boys" are fighting in Afghanistan, will not happen because our boys are supposed to be home by 2012.
So our boys will be home well before physical construction of any new nuclear submarines could begin. So taking money from our deployed troops to pay for nuclear subs isn't a choice we are being faced with.