Cathy Massiter, a former MI5 officer, resigned in 1985 and disclosed on Channel 4’s 20/20 Vision programme “MI5’s Official Secrets” that the security service had monitored trade unions, civil-rights organisations and the Campaign for Nuclear Disarmament (CND). In an affidavit and broadcast disclosures, Massiter said she had been responsible for CND surveillance from 1981 to 1983 and believed the operation was driven more by the group’s political importance than by evidence of a genuine security threat. She argued that the activity breached rules governing MI5’s conduct.
Massiter said MI5 analysed telephone intercepts involving CND chairman John Cox, including conversations with Joan Ruddock and Bruce Kent, and placed an informant, Harry Newton, inside the CND office. She also revealed surveillance of Harriet Harman and Patricia Hewitt while they held senior roles at the National Council for Civil Liberties. MI5 had classified CND as “communist controlled” from the late 1960s through the mid-1970s before downgrading it to “communist-penetrated”; Massiter said she found no evidence supporting suspicions that Kent was a communist sympathiser. The British government never officially challenged her revelations, though it traditionally declines to comment on intelligence matters.
