Elsewhere, rhetoric hints at a return of the expansion of nuclear arsenals across the world. In December, Russian President Vladimir Putin told a meeting of defence chiefs that strengthening nuclear capability should be a key objective for 2017. Donald Trump then took to Twitter to respond, vowing to do the same.

Such rhetoric has led to concerns about the world's nuclear capacity and the unpredictability of those in charge of the warheads.

It seems the world is a long way from "coming to its senses" - with millions of kilotons already in military service around the world.

Between them, the world's nuclear-armed states have around 15,000 warheads - the majority of which belong to the US and Russia.

It is estimated that just under 10,000 of these are in military service, with the rest awaiting dismantlement, according to the Arms Control Association.