Tell me about secret underground London.

A. Interesting question from peter.griff. He writes: 'One often hears about a secret subterranean London, whose existence is known only to a handful of people. Are there really government departments, BT tunnels and bomb shelters under the capital ' Thanks to href='http://www.theanswerbank.co.uk/People_and_Places/Question2404.html'>allen ives for his answer. He writes: 'There's a book called Secret London by Andrew Duncan, which might help.'

The question of underground London is a huge one, we should start with one of its most famous rivers.< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Q. The Thames

A. No. The Fleet, as in Fleet Street, once home to our national newspapers. It rises from springs on Hampstead Heath, fills ponds at Highgate and Hampstead, then goes underground for its last five miles. An anchor was dug up in the Fleet at Battle Bridge, near King's Cross, suggesting that it was once navigable. From there it flows down Farringdon Street, along the edge of Fleet Street before draining into the Thames beneath Blackfriars Bridge.

Q. And then there's the Underground itself

A. Yes. The Metropolitan Railway opened in March 1843. And, although hundreds more stations have been built since then, many have been shut. There are about 40 abandoned stations on the Underground network along its 255 miles of track.

Q. Where

A. Look out for Down Street, Mayfair, on the Piccadilly Line between Hyde Park Corner and Green Park. It closed in 1932. Churchill's war-time Cabinet is reputed to have met there. Or, if you're on a Tube train, look out of the window between Tottenham Court Road and Holborn on the Central Line and you'll see a station, unused since 1932. There's another 'ghost station' at Wood Lane, West London; at Brompton Road (used as an anti-aircraft command centre); and at Aldwych, in the heart of London.

Q. Many Tube stations were also used as air-raid shelters, weren't they

A. Yes, and some were specially extended. Eight deep shelters were built, all beneath underground stations and seven on the Northern Line. Each had two parallel tunnels 1,200ft long and divided into two floors. Four of the shelters, Belsize Bark, Camden Town, Clapham North and Clapham South, were fitted with bunks for 8,000 people. The other four, Goodge Street, Chancery Lane, Stockwell and Clapham Common, were kept for government use.

Q. Any other tunnels

A. Well obviously there are many train and road tunnels. But there's a Post Office one of particular interest.

Q. The Post Office

A. Yes, the Post Office atmospheric railway, built in 1929. The Post Office operates its own underground electric railway, known as Rail Mail, to take post from sorting offices to rail stations. Details of that are kept quiet for security reasons.

Q. And talking of security, where are the spooks' tunnels

A. I'm not really at liberty to say. However, Tottenham Court Road is meant to have six levels underneath it. Subterranean fortresses were also built during the 1930s to accommodate government officials during war. Four more were built later to prepare for the possibility of nuclear war and part of the Kingsway Tram Tunnel has been converted into an emergency control centre should there be a major disaster in London.

Q. Can I see any of them

A. Yes, or a few of them, any way. There's the Cabinet War Rooms, only a small part of the huge underground office complex beneath the Treasury building. This full complex has more than 200 rooms and is protected by 15ft of concrete. Many of the rooms are still in use as Government offices. It is known as Q-Whitehall.

Q. And these are the biggest

A. It seems not. A far bigger complex, it would appear, is the bomb-proof telephone trunk system built by the Post Office in the Cold War. Two tunnels lead from a building near Waterloo Station, to Trafalgar Square, the other to Faraday House in the City. A further tunnel connects telephone exchanges from Shepherds Bush in the West to Shoreditch in the east. It also connects with the Kingsway telephone exchange built 100ft under High Holborn in the early 1950s.

Q. And were the royal family well-protected

A. Again, there is a lot of speculation. These were, and indeed are, secret matters. But it seems there was a strong rumour that one of the Treasury tunnels has a branch that leads to Buckingham Palace. The royal family could use this to escape to Charing Cross and safety in the country. The tunnel runs from under the Mall.

Q. Any evidence for this

A. A huge extractor fan can be seen outside the gent's lavatories at the Institute of Contemporary Arts. The ICA says it's nothing to do with them. The building is opposite a top-security fortress building, on the corner of the Mall and Horse Guards Road, which is an entry to the Q-Whitehall complex.

Q. Can you recommend any books on subterranean London

A. Try these: London Under London by Richard Trench and Ellis Hillman; London's Disused Underground Stations and Abandoned Stations on London's Underground, both by J E Connor.

To ask another question about People & Places, click here