What lies beneath

E&T looks back at the fascinating history of London's Kingsway Tunnels - full of mystery and now up for sale.

There's nothing unusual about sitting in a London city office and hearing rumbling from the Central Line below. But pop through an unmarked blue door near to number 33 High Holborn, and you could find yourself in a lift heading down to a complex where Central Line trains rattle past overhead.

For here, 100ft under the city streets, hides a mile-long complex of horizontal and vertical shafts, fully equipped with electricity and water supplies and covering an area of 77,000 square feet. Known as the Kingsway Tunnels, the site has served as a bomb shelter for MI6 spies, a Public Records Office storage facility, and played host to the most important telephone line in the world. And like so much else in this hard-pressed financial era, it's up for sale.

Shelter from the storm

When the bombs rained on London during World War Two, Chamberlain's government declared that the Underground wasn't to be used as a ready-made bomb shelter. It was an instruction which, for effectiveness, ranks alongside his promise of peace in our time - the police wouldn't enforce the orders and, today, images of the temporary communities created in the Tube stations epitomise the spirit of the Blitz. By 1942, the government had backed down, and purpose-built shelters had been created at Camden Town and Clapham stations, among other places.

But the public weren't the first to be catered for when it came to deep-level facilities. The Kingsway complex had been completed in 1940, and was capable of providing shelter for 8,000 people but not the common herd. Most worked for government agencies - the Port of London Authority and the Ministry of Works among them - with the majority belonging to the Interservices Research Bureau.

While this sounds like a governmental typing pool, it was in fact a branch of the Special Operations Executive - part of MI6 - whose prime objective was to offer support to the Resistance in German-occupied countries. When the Bureau vacated the tunnels on 8 May 1945, it apparently stripped them clean of all its equipment, leaving no clue to the exact nature of its operations down there.

Over the following year, the tunnels were used by the Public Records Office as storage space for 400t of secret documents. But in 1946, the site transferred to the Post Office. The service had long had an interest in such facilities and was already running a 23-mile subterranean railway between the East End and Paddington. It wanted to expand its underground operations, but initially met resistance from the government. And then, in 1949, the Soviet Union detonated its first nuclear device, and everything changed.

With the dawn of the nuclear age came a perceived need to bury communications systems where they stood the best chance of surviving a nuclear strike. And so the government allowed the Post Office to press ahead with its development of what was already the deepest of any of London's underground networks.

Rooms without views

Having taken over the complex, the Post Office developed and enlarged what had officially been dubbed "tunnels 2147" and now became known as Kingsway.

Four tunnels were added, linked by smaller ones and graced with wooden road signs: 'First Avenue', 'Tea Bar Alley', and so forth. Even now, those markers are as much a clue to geography as the tunnels offer - their exact location in relation to the streets above remains secret, and Kingsway itself is actually hundreds of yards away. This caginess is in keeping with the Post Office procedure of giving geographically meaningful but deliberately misleading names to important facilities. More intriguing is the claim that the workers brought in to enlarge the site spoke no English, and had no idea where they were.

Kingsway - a 'non-director trunk tandem exchange' - became active on 30 October, 1954. It proved a remarkable operation. Being before the time of the subscriber trunk dialling code, long-distance phone calls required an exchange and Kingsway was Britain's largest, servicing over 13,000 lines and switching up to two million calls a week.

Its subterranean population of almost 200 occupied two main tunnels. Each a quarter of a mile long and 16-and-a-half feet wide, they housed three miles of racking carrying 337 miles of cable. As well as an artesian well, food, air conditioning, a canteen and emergency accommodation, the complex had four 1.5MW generators for standby power and a 22,000-gallon oil reserve, sufficient for six weeks' operation.

The wellbeing of staff was an obvious priority. Leisure facilities included a snooker hall, a bar and a tropical fish tank. The canteen even had 'windows', offering views of colourful landscape paintings.

As for safety, this was an important feature of life at Kingsway and nowhere more so than in the deep-level tubes housing the cables that ran into the exchange itself. Air pressure was constantly monitored and in the event of its falling below 1,000 millibars, flashing lights and sirens demanded evacuation. A Thames flood warning produced a similar reaction. After a two-man patrol had determined that the tubes were empty of personnel, the bulkhead doors would be closed, sealing the tubes until the all-clear was given.

It's good to talk

Once in operation, Kingsway continued to develop and in 1956 it became the London terminal of the first transatlantic telephone cable. This was a complicated operation, involving linking three sites - Kingsway, the Wood Street international exchange and the Continental exchange in the Faraday building - with several hundred copper pairs, the twisted copper strands used for the transmission of analogue telephone signals. This was to give Kingsway an important role following the October Crisis of 1962, when the US and the USSR faced-off over the stationing of nuclear missiles in Cuba. Engineers, technicians and support staff remained in the tunnels for days, preparing for the possibility of nuclear war - in the event of which, their job would have been to keep the phones working.

While good sense prevailed on that occasion, the near-endgame of the period made it clear that it's good to talk. With satellite technology not yet available, the resulting 'hot line' link-up between the White House and Kremlin made use of the Atlantic cable and was routed directly through the main distribution frame in the Kingsway Tunnels.

If more direct means of inter-governmental communication have long been in place, that hasn't put an end to Kingsway's usefulness as a secure facility.

After the privatisation of the Post Office in the early 1980s, the tunnels became home to British Telecom's London Area Group, which operated and serviced CCTV systems across the capital, as well as providing back-up services for Icarus (BT's International Circuit Allocation Record Update System).

Questions remain...

Over the past decade, and largely as a result of technological advances, BT's operations in the tunnels scaled down and eventually came to a halt. They're now up for sale, though speculation that they might host an underground capsule hotel is without foundation: the necessary health and safety permits won't be forthcoming.

The ongoing sale has resulted in greater access being granted not only to potential buyers but also to journalists, and some interesting observations have been made. In an Evening Standard blog, Richard Godwin noted that an electrical diagram on the wall incorporated the old newspaper offices on Fleet Street. Perhaps the Kingsway Tunnels were used to eavesdrop on journalists' calls, as well as facilitate them?

But that's just one of the questions about Kingsway that nobody will answer.

For more information on the Kingsway Tunnels, visit Subterranea Britannica's website [new window] and read Duncan Campbell's 'War Plan UK' (Burnett Books, 1982).

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