The Public and Commercial Services Union or PCS, is the British Trades Union which represents the interests of civil servants in the Executive, Admin and Support grades of the British Civil Service. (The senior civil servants are represented by the First Division Association and the scientific and professional grades by Prospect; this sort of thing matters in the British Civil Service.)
The Union is the end product of a series of mergers between various public sector unions over the past fifteen years; in 1988 the Civil Service Union and the Society of Public Servants combined to form the National Union of Civil and Public Servants, which itself merged with the Inland Revenue Staff Federation in 1996. The resulting Public Services, Tax and Commerce Union (or PTC) then joined with the the Civil and Public Servants' Association ( or CPSA) in 1998, and the Public and Commercial Services Union was born.