A few weeks ago, I experienced a power cut at home. It was a strangely nostalgic experience, as I realised everything from the lights to the TV had gone down. Although I am too young to remember doing my homework by candlelight during the three-day week (as my older sister claims), blackouts were a frequent occurrence in my late 1970s childhood.

However, after the initial fun of scrabbling around for candles, and telling the kids we were having cold baked beans for supper, the novelty soon wore off as I realised my day wasn’t being curtailed just by the lack of hot food and water, I was also suffering from loss of income — I couldn’t work without a computer and wifi. We are far more reliant on electricity than we were in the 1970s.

The power came back on in less than two hours, but it did make me question my lack of preparation for something more serious. My cupboard under the stairs is mostly made up of rusty tins of paint. The government recommends that each household has a box containing a first aid kit, wet wipes, wind-up torch, power bank for your phone, camping stove, bottled water, tinned goods and a can opener.

That is according to the official Prepare website, launched just days before the general election of 2024, which managed to perfectly capture the retro 1970s vibe that has engulfed the UK in recent years — not just high taxes, struggling public services and chaotic government, but the mild state of paranoia that pervaded that grim decade. I have no idea if there is a new prime minister as I write this on a manual typewriter in my bunker, trying to tune into the (soon to be disbanded) Radio 4 longwave.

I am being only slightly flippant. As the King said this week at the opening of parliament: “An increasingly dangerous and volatile world threatens the United Kingdom.” However, nowhere in Prepare’s quite long list of instructions and warnings about possible catastrophe does it mention the need for cash. This is a curious omission.

If Russia or Iran decides to launch a full-scale cyberattack on Britain — and that is far more likely than them sending a nuclear weapon our way — surely having a few £20 notes among the medical dressings and the tins of spam would be quite useful.

A rocket hitting Romford or a drone attacking Droitwich Spa is not going to happen, I hope. The tills of your local supermarket crashing and consumers being unable to pay for their evening meal is highly probable, however. We know this because Marks & Spencer, Co-op, Jaguar Land Rover and Heathrow have all been hit recently. Last year Ian Stuart, the UK chief executive of HSBC at the time, told MPs: “We are being attacked all the time.” It will not be long before a group of Putin-backed terrorists get through a major financial institution’s defences and jam up the UK digital payments system either in a small, annoying way or possibly on a more serious scale.

It seems a significant minority of Britons have taken matters into their own hands. According to a survey by the ATM operator Link this week, 15 per cent of people have an emergency stash of cash at home.

They are not loopy doomsday preppers, or at least not all of them are. If anything, they are in line with sensible, western European governments, who have decided that holding on to some hard currency might be quite useful. The Dutch central bank strongly advises citizens to store €70 per adult and €30 per child as part of an emergency preparedness campaign to ensure households can last 72 hours without ATMs, internet banking or digital payment terminals.

A more interesting case is Sweden, which with other Nordic countries, pioneered digital payments. The deputy governor of its central bank predicted in 2018 that it would be an entirely cashless country by 2025. This has not come about, but a mere 5 per cent of payments are made using cash, much lower than the UK’s 9 per cent. Stockholm’s tram network, cafés and museums run almost entirely on digital payments. If you don’t have a smartphone, you are going to struggle in Sweden.

But Sweden’s defence ministry recently sent every home a brochure entitled If Crisis or War Comes, advising households to use cash regularly and keep a minimum of a week’s supply in various denominations to “strengthen preparedness”. Norway has brought in legislation that means retailers can be fined or sanctioned if they refuse to accept cash. The thinking behind this is that if too many outlets refuse to take notes and coins, this form of currency will stop having, well, currency.

A campaign group called the Payments Choice Alliance would dearly like Britain to follow suit. But, according to Link, 14 per cent of shops turned entirely cashless over the last year.

I am not nostalgic for cash — I find the polymer notes a slippery menace. Money is a philosophical construct based on trust. John Maynard Keynes used the example of the Micronesian island of Yap, where islanders used vast 4-ton rai stones as currency, to prove the tokens humans use for financial transactions often have no intrinsic value.

It doesn’t really matter what we use, but we do need a backup if — or almost certainly when — a malicious force decides to disable our digital payment networks. It may only be for a morning or a day, but I’d like to be able to pop to the corner shop and buy a pint of milk. And I think Raj would prefer I pay with a fiver than with a large hunk of rock. If we stop using cash entirely, we may find an outage becomes much more than an inconvenience.