Trump alone, a deranged demagogue, has the power to launch US nuclear weapons. That must change. No one person should have that capacity, least of all a tyrant. But it's also a reminder of the folly of possessing nuclear weapons at all. As the Treaty on the Prohibition of Nuclear Weapons enters into force on January 22 we should celebrate. Then we must get back to work to persuade the nuclear pariah states to do the right thing and disarm.