Leif Mills was educated at Balliol College, Oxford. He served as a trade union offi cial with the Banking, Insurance & Finance Union (formerly the National Union of Bank Employees) for thirty six years. For thirteen years he served on the TUC General Council, becoming TUC President 1994 - 95. He was also a member of the Monopolies & Mergers Commission for nine years and the Armed Forces Pay Review Body for seven years. From 1998 to 2005 he was Chairman of the Covent Garden Market Authority.
