THE MINISTRY of Defence "Electronic Test Facility", a rather mysterious 150-ft high tower stands isolated in a British Nuclear Fuels Limited site at Capenhurst, Cheshire.
Locals knew that the tower housed a dark secret but did not know what it was. That secret is now out.
The tower was craftily erected between two BT microwave radio towers carrying telephone traffic. The ETF was the ideal place to discreetly intercept international telephone calls of the Irish government, businessmen and those of suspected of involvement with IRA terrorism.
Channel 4 filmed extensive BT equipment inside the building, including optical fibre cables linking the tower to the MoD's communication system.
The hi-tech white ETF tower included eight floors of advanced electronic equipment and three floors of aerial galleries.
These were used to extract and sort the thousands of communications passing through every hour. Fax messages, e-mails, telexes and data communications were automatically sorted by computers scanning their contents for key words and subjects of interest. Telephone calls could be targeted according to the numbers dialled or by identifying the voice of the speaker.
At the time the tower first came into operation the IRA campaigns were raging.
Relations between the British and Irish government's were not always smooth, with the British suspecting their Irish counterparts of being sympathetic to the IRA.