The precise locations of dozens of secret military and spy bases are to be revealed on Ordnance Survey maps for the first time, ending one of the last remaining legacies of the Cold War.
For decades, tourists and ramblers have stumbled across secret radar bases, nuclear bomb stores and rocket testing ranges tucked away in quiet woods or remote hillsides because they had been "airbrushed" out of even the most detailed official maps.
But the Government's security chiefs have quietly abandoned that policy by scrapping its list of secret military and intelligence facilities - known officially as the "sensitive sites register". The decision was made earlier this year by the Cabinet Office but never formally announced; it acknowledged that the internet had defeated its attempts at secrecy.
Aerial and satellite photographs of the country are available on the internet, while web-based mapping services such as Multimap are competing directly with Ordnance Survey (OS). The change in policy means the last remaining 50 sites on the register - including the nuclear warhead factory at Burghfield in Berkshire - will now be marked on all the maps printed by OS.
The obsession with secrecy, which deepened once spying by the Soviet Union intensified during the Cold War, has been relaxed recently. The "sensitive sites register" has been slowly whittled down and OS has begun including some sensitive sites on its most detailed Explorer series of maps, but anomalies remain.
In western Scotland, buildings and railway tracks for Glen Douglas armament depot near Faslane nuclear submarine base are marked but unnamed on the most detailed Explorer maps, but are "airbrushed" out of the larger-scale touring maps. A rocket testing range in Wyre Forest near Kidderminster, Worcestershire, is shown by an unnamed rectangular field in the detailed maps, but omitted in all large-scale maps.
Some of the most sensitive sites will still not be named or will have misleading labels such as "disused airfield" or "depot". But the decision is a victory for anti-secrecy campaigners such as Alan Turnbull, an internet enthusiast who first exposed the availability of this apparently secret mapping data on the web.
Mr Turnbull built his own site, www.secret-bases.co.uk, in August 2003 with the reluctant agreement of the military. He said yesterday he was "pleasantly surprised" at the Cabinet Office decision - particularly after Lord Falconer, the Lord Chancellor, said last week he wanted to restrict access under the Freedom of Information Act.
"It seems that there's some back-pedalling going on in Government about freedom of information, and this is an important step to counter that," he said. "It's nice to think the Cabinet Office has been pushed along a little bit by my highlighting this in such a public manner."
A spokeswoman for the Cabinet Office confirmed: "The decision was taken because of the availability of this information from open sources."
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