Jimmy Hoffa Agreement. He played a major role in the growth and development of the union, which eventually became the largest (by membership) in the United States with over 2.3 million members at its peak, during his terms as its leader. Hoffa became involved with organized crime from the early years of his Teamsters work, and this connection continued until his disappearance in 1975. He was convicted of jury tampering, attempted bribery and fraud in 1964, in two separate trials. He was imprisoned in 1967 and sentenced to 13 years. In mid-1971, he resigned as president of the union as part of
GCHQ trade union ban in Cheltenham. Following the expression of concern by US spymasters, trade unionism was banned at GCHQ (which monitors radio communications around the world as a part of an Anglo-American intelligence agreement). The US security agency used its diplomatic influence to secure the union ban. Margaret Thatcher claimed industrial action at the base, particularly during the 1981 civil service pay strike, had undermined the nation's security and justified the ban. On 25 January 1984, during the Second Thatcher ministry, Foreign Secretary Geoffrey Howe announced in the House of Commons that trade unionism was no longer acceptable at GCHQ. The TUC, CCSU,