Inside London's secret bunker

The mammoth Kingsway Telephone Exchange, 100ft below High Holborn, has had a fascinating but top secret life since it was first created in the Second World War as one of a system of deep-level bomb shelters.

And now that it’s up for sale, British Telecom have opened it up for interested journalists and investors (I come under the former category). For my pictures, click through the gallery at the bottom of the page.

The shelter was originally built, we are cryptically told, by ‘non-English speaking Europeans’ in 1942 who didn’t know what they were building or where it was located. It was used by MI6 and the Public Record Office after the war and then expanded by th Post Office to become one of British Telecom’s secret underground telephone exchanges – deliberately given the misleading name Kingsway even though is closer to Chancery Lane. Rendered obsolete in the 1980s, it was refitted to provide shelter as a potential site for the Government in case of nuclear war. For the full history, see the excellent Subterranea Britannica. For personal recollections of what it was like to work there, click here.

I went down there this morning courtesy of BT and was stunned to see that was it built on such a massive scale. It had its own artesian well, power generators, sleeping accommodation, six-months' food supplies, a funky 1950s recreation room and a canteen – the complex was actually ‘closed down’ for the Cuban Missile Crisis , during which time up to 200 workers were locked in for the duration of the scare.

The original tunnels, two of them, run parallel for a quarter-of-a-mile beneath High Holborn – beneath even the Central Line, which can be heard rumbing overhead. Off these main tunnels are four smaller tunnels that were built by the Post Office after the war, each about the size of a football pitch and one of which once store a small rowing boat that was to be used if there was flooding in any of the other BT exchanges.

The telephone engineers who worked down here and couldn't escape to the surface for lunch also kept snooker tables and a tropical fish tank to help them pass the time, in between maintaining the interchange for the world's first transatlantic phoneline, which helped connect the White House and the Kremlin.

The existence of the complex became public knowledge in 1972 and although no civilian ever managed to break in (and many tried such as notorious underground explorer Duncan Campbell, who wrote about Kingsway here), horror writer James Herbert managed to produce an accurate description of the complex in his novel ‘Domain’. You might want to check it out before you lodge a bid for the exchange with Farebrother Chartered Surveyors.