How Britain and the US keep watch on the world

From the National Security Agency's imposing headquarters at Fort Meade, Maryland, ringed by a double-chain fence topped by barbed wire with strands of electrified wire between them, America "bugs" the world.

Nothing politically or militarily significant, whether mentioned in a telephone call, in a conversation in the office of the secretary general of the United Nations, Kofi Annan, or in a company fax or e-mail, escapes its attention.

The NSA costs at least $3.5bn a year to run. It employs at least 20,000 officers (not counting the 100,000 servicemen and civilians around the world over whom it has control). Its shredders process 40 tons of paper a day.

Its computers - measured in acres occupied by them rather than simple figures - "vacuum the entire electromagnetic spectrum", homing in on "key words" which may suggest something of interest to NSA customers is being conveyed.

el - a review of NSA without mentioning "project echelon" by name.