Hi-tech fortress where secrecy reigns supreme

The MI6 building is known to some staff at Vauxhall Cross as "Ceausescu Towers", after the former Romanian dictator with a penchant for grandiose and inhuman architecture.

The MI6 building is known to some staff at Vauxhall Cross as "Ceausescu Towers", after the former Romanian dictator with a penchant for grandiose and inhuman architecture.

Designed by the Terry Farrell, who was unaware of the intended tenants, it originally cost £240m to build. But to accommodate its occupants a further £86m of public money needed to be spent to cope with the service's needs.

The building, which opened in 1994, includes a shooting range and arsenal, a garage for adapting and maintaining MI6's fleet of special cars, secure areas where eavesdropping is impossible, and a array of computer and radio communication rooms. There are rooms for the development of specialist espionage equipment of the type made famous by "Q" the fictional boffin of the James Bond films, and a forgery section where counterfeit documents are produced.

Details of the building are covered by the Official Secrets Act which every member of the staff is obliged to sign. The former MI6 officer Richard Tomlinson, who now lives in Italy, visited the building many times before he left the service in 1996. "If I told you what was in the building I would be open to prosecution," he said yesterday.

Whitehall security chiefs have long been aware that MI6 headquarters is a prime target for attack, especially for propaganda purposes, and it is designated HPT - high potential physical threat.

The exterior walls and windows of the building have been modified to minimise the effects of a bomb or missile attack. The windows are triple-glazed to guard against laser and radio frequency flooding techniques, and there is special shielding to prevent enemy access to the computer system. For top secret meetings there is a special "silent" room.

According to the author Stephen Dorrill there is also a secure command and control room to run major operations such as the pursuit of war criminals in Bosnia. On the lower ground floor there are interview rooms for debriefing defecting spies such as the former KGB colonel Vasili Mitrokhin.

At the top of the building is an array of radio and satellite equipment that enables the service to communicate with its offices around the world. If MI6 wants to communicate with an officer under deep cover, say in Russia, it will send a radio message that will be compressed at the Moscow MI6 station and transmitted in a data burst as the agent drives past.

On a second floor is a powerful computer set-up in which all the data sent in by MI6's officers and spies is collated. This is the information that enables MI6 to produce the CX reports - the weekly intelligence briefings that go to the Prime Minister and Foreign Secretary.