Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (Known as the 'GCHQ' case, this case will be discussed at several stages during the course.) Acting pursuant to delegated prerogative power, the Minister for the Civil Service (the then Prime Minister, Margaret Thatcher) issued instructions, altering the conditions of service of civil servants employed at the Government Communication Headquarters (GCHQ) in Cheltenham. These effectively prohibited them from being members of a trade union. Judicial review of the decision was sought by the CCSU on a number of grounds and the key issue became whether the courts could review the exercise of prerogative power. The House of Lords held, in a landmark decision, that the way in which prerogative power was exercised by government could be subject to judicial review.