Russia nuclear threat explained - from 30-minute warning to where Putin keeps codes

The world is once against fretting over the spectre of nuclear war. But should we take Putin ’s threats seriously, or dismiss them as desperate bluffing as his Ukrainian adventure falters.

Here former British Army chemical and nuclear weapons expert, and author of Chemical Warrior, Hamish de Bretton-Gordon, and Professor Anthony Glees, a security expert from the University of Buckingham, answer your questions.

What did Putin mean by placing Russia’s nuclear weapons 'into a special mode of combat service'?