A former director general of development, concepts and doctrine at the Ministry of Defence has told talkRADIO that he believes the very existence of nuclear weapons is what’s keeping them from being used.
Parliament is today voting on the future of Britain's Trident nuclear weapons programme, and whether it should be renewed.
The shadow foreign secretary Emily Thornberry has claimed it would be "reckless for us to plough ahead with the most expensive of all the various options", while the CND have questioned whether the £205 billion cost of renewing Trident is justified.
But Rear Admiral Chris Parry told Sam Delaney: "That's like saying there's a cheaper alternative to a Rolls Royce, a push bike.
"The powers that would probably want to go to war with each other over various things have been restrained by the fact they have nuclear weapons pointing at each other."
Listen to the full interview to hear him tell Sam how Trident works, and why he believes Britain needs it