A taste of how the other half lived in the Blitz

There are pensioners living in London who can recall long, uncomfortable nights during the Blitz, huddling in the Underground as bombs rained down their homes. With thousands crammed together in confined spaces, you could meet all sorts of people but you never saw a spook from the Interservices Research Bureau, a branch of MI6, or from other government agencies such as the Port of London Authority or the Ministry of Works engineering unit. They had somewhere better to hide.

There was a secret lift behind an unmarked door near 33 High Holborn, where the Daily Mirror used to have its head office. Even Fleet Street's finest did not know who used it, or where it led. In fact, it took selected officials to the safety of two secret tunnels, deep below London, with a total length of about half a mile. They were so far below ground that, as I walked along them yesterday, I could hear Tube trains rumbling along the Central Line way above. These tunnels, which became even more important in the Cold War than they were during the Blitz, stayed on the "secret list" until three years ago. Officially, they did not exist or, if they did exist, they were not located under High Holborn but somewhere else. In the archives, you might find a reference to "tunnels 2147". To those who were allowed to know, such as the 200 or so security-vetted staff employed in them, they were the Kingsway Tunnels – a deliberately misleading name, because Kingsway is hundreds of yards away.

Now the secrecy has been partially lifted, and the tunnels are up for sale to anyone imaginative enough to be able to find a commercial use for subterranean real estate. They are owned by the property arm of BT, which has no further use for them. I was among the journalists allowed to go down for a privileged glimpse of a bit of 20th-century history.

Even now, you will not find the entry door unless you know where to look. Somewhere in the tunnels, our guide Richard Bamford, a senior BT technician, was asked which road we were under. "I know but I'm not telling you," he said. "If somebody wanted to buy this as a semi-secret location for bank servicing, would they want you to know that information? Probably not."

This would be a fabulous place to open a nightclub, but health and safety laws would never permit it. Likewise, a hotel, offices or living accommodation are out. Somebody should grab the chance to use the tunnels as a film location, because they are eerie, dated and full of places to hide away from the bad guys. Although much of the kit in use there in the post-war era has been removed to museums, I saw enough relics to make it a trip back in time. There were machines bearing names of manufacturers long since wiped out by mergers and recession, such as English Electric (Stafford), Metro-Vickers, Hackbridge and Hewittic Electric, and Ruston and Hornsby. The huge tubes forming the walls of the main tunnels bear the initials LPTB, meaning they were built by the old London Passenger Transport Board.

The two wartime tunnels that kept the men in bowler hats safe from the Luftwaffe were supplemented in the 1950s by four more, about half as long as the originals, added by the Post Office, who turned the site into a vast telephone exchange. The large tunnels are linked by smaller ones, and the sense of being in an underground town is heightened by the wooden roads signs that tell you which tunnel you are in – "South Street", "First Avenue" or "Tea Bar Alley" etc. A menu board is still on the wall in the old staff restaurant, offering sausages, chips, tea and sweets

During the Cuban Missile Crisis of 1962, when the world hovered on the brink of nuclear war, dozens of engineers, technicians and support staff were literally entombed in the tunnels, forbidden to go up to ground level for days. Their grim task would have been to keep phones working after London was obliterated by a nuclear bomb. They had emergency generators to keep the machines, lights and air conditioning going independently of whatever horror was being experienced above. They also had a well-stocked bar and restaurant, a recreation room with a snooker table, a private cinema and an artesian well for fresh water.

When the crisis was over, the US and Soviet governments realised how near they had come to catastrophe without being able to speak directly to one another, so it was decided there had to be a "hotline" between the White House and Kremlin to allow John Kennedy and Nikita Khrushchev to talk by telex in the days before satellite technology. The connection had to go under the Atlantic and overland until it reached the Main Distribution Frame that is still down there, in the tunnel called Third Avenue, where it was boosted and passed on.

Although I was the first journalist allowed in the tunnels, I was not the first to ask about them as the secret of their existence spread. In the 1980s, the investigative journalist Duncan Campbell, then of The New Statesman, did not take no for an answer. John Tasker, the former manager of the Kingsway Tunnels, said: "He had an obsession about government secrecy. He phoned BT security one Christmas and told them 'if you go down, you will find a Christmas tree'. He had planted it. They still don't know how he got down there."

It must have been a curious life, working deep underground every day, but Ray Gapes, a BT engineer, recalls it fondly. "When I arrived in 1970, when I was 18, it was a fantastic place to explore," he said. "There is a lot of nostalgia for me, coming back here. It was a good, comfortable existence working down here. There was a slightly dusty smell but it was clean."