With their whitewashed seafronts and jangling arcades, there are few better symbols of British national life than its seaside towns. Yet, in a handful of those sleepy coastal communities can be found one of the most serious, and overlooked, security threats.

When we send an email, use a mobile or make a bank payment, most of us have a vague idea that it speeds to its destination via wireless signals, perhaps bouncing off a satellite en route. But the truth is that 97 per cent of global communications travel along a network of just 200 fibre-optic cable systems that run along our oceans’ floors. This physical network is the indispensable infrastructure of the 21st century. Thin as hosepipes, these cables carry some $10 trillion (Dh36.78 trillion) of financial transactions a day and underpin the operation of every computer in the world. But they are vulnerable.

Their deep-sea locations are both isolated and publicly available. Their routes often concentrate at specific choke points, and severing them would require little expertise. Either on land or sea, these jugulars of the world economy are a singularly attractive target to our enemies — whether they be an increasingly bellicose Russian navy or a terrorist group. A successful attack has the potential to cripple Britain’s security and prosperity. Undersea cables have typically been installed and owned by private companies ever since the first was laid under the Atlantic in 1858. This means that most states have not given the network the priority attention it merits.

The main threat comes from the sea. Russia is investing in its navy and especially in submarines capable of damaging undersea cables undetected. Moscow’s increasing technical capability is matched by a display of maritime belligerence not seen since the Cold War. US intelligence officials have identified a sustained pattern of Russian submarines “aggressively operating” near the busiest data highway in the world between New York and London.

The Taiwan earthquake in 2006 shows the sort of damage that any disruption can cause. Underwater landslides severed cables, regional currency markets ground to a halt, Hong Kong lost almost all communications and millions of mobile phones instantly cut out. With both the prime minister and the chief of the National Cyber Security Centre highlighting new, unconventional forms of Russian aggression, these risks must be taken seriously.

The second threat is on land. For commercial and geographical reasons, undersea cables tend to come ashore at just a few remote sites, presenting terrorists with an easy way to cripple internet capacity. According to documents released by WikiLeaks, the United States State Department considers several United Kingdom cable landing sites to be as “critical” to American security as its military facilities — except they are protected by little more than a skeleton team of techies and a sturdy gate. They are particularly vulnerable to attack.

Yet, as I set out in a Policy Exchange report, there are some quick steps that can be taken to improve Britain’s resilience. Security at cable landing sites should be beefed up. Like Australia, Britain could establish Cable Protection Zones in sea corridors to better police maritime activity. Private companies should install monitoring equipment on their undersea cables, as well as “dark cables” to provide emergency capacity. Furthermore, as one decides on the UK’s future defence priorities, it is paramount that the freedom of the seas and sea lanes of communication are protected.

Britain and her Nato allies must ensure that their maritime capabilities get the investment they need to counter these new, unconventional threats. When Russia annexed Crimea, one of its first moves was to take control of the peninsula’s primary cable exchange and sever its main connection. It is a precedent Britain should heed.

In the information age, a country’s security and prosperity rest on its ability to communicate effectively with the world. Unless we act now, our century’s greatest innovation could be its undoing.

— The Telegraph Group Limited, London, 2017

Rishi Sunak, a Conservative Party politician in the United Kingdom, is the member of parliament for Richmond. He is the author of Undersea Cables: Indispensable, Insecure.