UN chief Antonio Guterres stared into the camera and issued a grim warning. "The clouds that parted following the end of the Cold WarA period of diplomatic conflict between blocs led by the USA and the USSR that lasted from 1947 until 1991, when the USSR collapsed. are gathering once more," he declared. "Today, humanity is just one misunderstanding away from nuclear annihilation." 

Tensions are running high in the Middle East. PyongyangThe capital of North Korea. In the early 20th Century it was a centre of Christianity known as the "Jerusalem of the East". is entrenched in an endless battle over the future of the Korean peninsula. And in February, Russia put its nuclear weapons on high alert following its shock invasion of its neighbour, Ukraine. 

"We have been extraordinarily lucky so far," Guterres continued. "But luck is not a strategy." 

Guterres' audience was a conference of the Non-Proliferation Treaty (NPT0, an international treaty from 1970 that aims to prevent the spread of nuclear weapons. He believes that the answer to any impending crisis is international cooperation and working together to rid the world of nuclear arms. 

But some say a different strategy is needed. Should the treaties fail, humanity will need a backup plan. 

It would not be the first time that preparations have been made for a nuclear catastrophe. During the height of the Cold War, the British government made a plan to prepare the West for nuclear warfare. It was called the Wintex-Cimex plan, and it envisaged a scenario that looked something like this: 

Friday, 13 March 1981. The Soviet Union has invaded Yugoslavia. Within days, the Labour leader and the Archbishop of Canterbury are arrested at a peace march in Trafalgar Square. After British military bases are bombed, the United Kingdom unleashes 29 nuclear missiles on the Soviet Union.

On the morning of 21 March, the Queen delivers a speech to the nation announcing the beginning of World War Three.

"Not for a single moment did I imagine that this solemn and awful duty would one day fall to me," she reads.

A booklet, issued in 1980, includes advice on how to paint windows white to reflect the heat from radioactive blasts, alongside tips on how to label and store dead bodies. Some people built bunkers, stocked with piles of tinned food. 

At the time, many ordinary people felt the fear of nuclear war. "I hid under my blankets when I went to sleep for about six months, waiting for the missiles to drop on my house and melt my Star Wars toys," said Justyn Taylor, who grew up in Cardiff in the 1980s.

Today, the source of the threat is different. It is Russia, not the Soviet Union, that is the focus of the wary eyes of the West. The sense of security that emerged in Europe after the fall of the Berlin Wall has been shattered by the conflict in Ukraine. But nobody can say for sure who, if anyone, will be the first to push the nuclear button.

Just one thing is clear: the stakes are high. The future of humanity depends on what happens next. 

Yes: This is a dangerous time for the entire world. It would only take one misstep to start a terrible war. It is better to have a backup plan that you never use than to have no backup plan at all. No: This is alarmist. There are actually 47,000 fewer nuclear weapons in the world today than in the mid-1980s. And even Vladimir Putin admits that a nuclear war would have "no winners".Or... We should not underestimate the seriousness of this threat. But instead of building nuclear bunkers, we should focus on working together to eliminate the danger and rid the world of nuclear weapons.