The Air Force was also seriously against permissive action locks. When forced to add them, the generals made the launch codes the same on every warhead, all zer

The Air Force was also seriously against permissive action locks. When forced to add them, the generals made the launch codes the same on every warhead, all zeros. Command and control is very hard: being able to always and immediately launch a nuclear attack but never subject to an unauthorized launch presents a variety of challenges. PALs help with the latter but not the former. Maybe because the Brits have fewer warheads (and therefore the ability to exercise more control) or needed to respond faster (being closer to the USSR and other nuclear powers), they made a strategic choice to skip PALs. Eric Schlosser's book Command and Control is worth a read if you are interested in the history of the US nuclear arsenal.