You could always go on changing things but there comes a time when you have to decide to stop.

According to his memoirs he then was either responsible for or intimately involved with the development of some of the basic techniques of ELINT for example:
Operation ENGULF: acoustic cryptanalysis of Egyptian Hagelin cipher machines in 1956;
Operation RAFTER: remote detection of passive radio receivers used by Soviet agents through detecting emanations from the local oscillator in 1958 (a technique now more commonly used to enforce payment of television licences); and
Operation STOCKADE analysis of compromising emanation from French cipher machines in 1960. Wright went on to publish The Encyclopaedia of Espionage in 1991 which had little impact. The Central Intelligence Agency sought Marconi's assistance over a covert listening device (or "bug") that had been found in a replica of the Great Seal of the United States presented to the U.

Spycatcher was part memoir part exposé of what Wright claimed were serious institutional failings in MI5 and his subsequent investigations into those. He is said to have been influenced in his counterespionage activity by James Jesus Angleton the US Central Intelligence Agency (CIA) counterintelligence chief from 1954 to 1975.