War may be coming. Are we psychologically ready?

If the UK suddenly found itself at war, would you know what to do? Do you know what would be expected of you?

The Government wants us all to start preparing for severe disruption to our lives. It wants us to stockpile canned food and drinking water, strengthen our civic resilience, and plan for the possibility of war.

Work has begun on the government's so-called "war book", which hasn't been updated in decades.

The UK's most senior soldier has sounded the alarm. The Chief of the Defence Staff Sir Richard Knighton this week said the threat from Russia meant Britain was living through the "most dangerous" period of his 35-year career in the armed forces.

But what is the threat? In 1940 the danger of a German invasion of the UK was very real. But the chances of Russian tanks rolling up Whitehall are surely negligible.

"It's not the tanks you need to worry about," says historian Margaret MacMillan, author of War: How Conflict Shaped Us.

"It's the cutting of cables on the ocean floor. It's the hacking into systems on which so many things depend. The possibility for asymmetric war, for cyber war, is growing by leaps and bounds."

But are we ready? After 80 years without war on our own soil, are we, as a society, psychologically prepared for it? Are we ready to approve large increases in defence spending, and for the sacrifices that that might entail in other areas of our national life? Or does the threat seem too far-fetched to be real?

"I think we have become used to the idea that peace is the normal state of affairs, that it's going to last," says McMillan.

"So no, I don't think we are psychologically prepared… but I do think that we are beginning to recognise that war is something that is closer to us than we'd like to think".

Archive film footage showing Britons in 1913 enjoying days at the races or watching the cricket contrasts sharply with what followed during the horrors of World War One.

"In a sense it's now a bit like those Edwardian summers before 1914, when there was a lot of talk of war but the notion of actually going to war seemed so far-fetched as to be beyond belief and I think that's where we are at the moment," says retired British General Sir Richard Shirreff, a former Deputy Supreme Allied Commander Europe.

Europe has not always been so war-averse. In 1914, recruitment stations were flooded with volunteers eager to serve their country. In Britain, that generation was raised on heroic tales of empire-building, in which war was one glorious cavalry charge, leading to swift victory and everyone home by Christmas.

But the experience of what came to be known as the Great War seared itself into the popular consciousness and survives in our collective imagination.