MP's have voted overwhelmingly to renew our Trident nuclear weapons system and the first job of any new prime minister is to write the "letters of last resort" which contain prime ministers' instructions for what to do in the event of a nuclear attack. The handwritten notes are taken to the UK's four Vanguard-class submarines, the ships which carry the ballistic missiles the Royal Navy calls "the nation's ultimate weapon" and contain instructions of what to do in the worst-case nuclear scenario: the obliteration of the UK state. The value of nuclear weapons is in their deterrence - the promise of mutually assured destruction. Theresa May has told the Commons that she wouldn't hesitate, but she could do no other. It is rumoured previous prime ministers may not have been so certain. By their nature the letters have to make broad moral judgments rather than situationally-dependent ones. They're about morality and ethics, not tactics. In the event that deterrence fails and we are attacked, would it be moral to use our nuclear weapons against civilians in retaliation? What would you do in the event of nuclear war? Under the 1949 Geneva Conventions, collective punishment is a war crime. If you think the moral principles of collective punishment are clear when it comes to nuclear weapons what about in other stories in the news? Is it always wrong to punish the innocent in pursuit of a wider justice? Should we ban all Russian athletes from the Rio Olympics to punish the drug cheats? Is protecting American citizens against terrorist attacks a greater good than the right of Muslims to travel to the USA? The morality of retaliation and collective punishment on the Moral Maze. Witnesses are Major General Patrick Cordingley, Air Vice Marshall Nigel Baldwin, Avia Pasternak and Austen Ivereigh.