Born in Croydon, Surrey Priestley was educated at St Boniface's Catholic College, Plymouth, and Balliol College, Oxford, graduating in 1972 with an honours degree in philosophy, politics and economics (PPE). He was president of the Oxford Union and chairman of the Oxford University Labour Club. He stood twice for Labour in Plymouth in general elections (once against David Owen. From 1974-76 he was president of the Young European Federalists.
Priestley has been an Official of the European Parliament since 1973, first as Administrator, then Principal Administrator with the secretariat of the Committee on Budgets 1973-83, Chairman, Staff Committee of the European Parliament (1981–83), Head of Division of the Committee on Energy, Research and Technology 1984-87, Co-chairman of the Staff Regulations Committee of the EC (1985–87), Director in the Directorate General of Committees and Interparliamentary Delegations, responsible for budgetary affairs and the single market 1987-1989, Secretary General, Socialist Group, European Parliament 1989-94, Director, Private Offices of the President of the European Parliament 1994-1997, and Secretary General, European Parliament from March 1997 until March 2007
The Secretariat of the European Parliament is the administrative body of the European Parliament headed by a Secretary-General. It is based in the Kirchberg district of Luxembourg and around the Brussels-Luxembourg Station in Brussels and employs 4000 officials. He was knighted in the Queen's Birthday Honours List, 2007 and was asked to participate in the second Irish referendum campaign on the Lisbon Treaty. He is the author of Six Battles That Shaped Europe's Parliament" (2008).
- KCMG appointment, Birthday Honours 2007 (16 June 2007 supplement)
- "Julian Priestley to step down as Secretary-General of the European Parliament". Europarl.europa.eu. 24 October 2006. Retrieved 7 March 2011.
- "Curriculum Vitae". Google. Retrieved 7 March 2011.
- "Six Battles that Shaped Europe's Parliament". John Harper Publishing. 6 April 2008. Retrieved 7 March 2011.