The extensive Thatcher archive consists of political and personal papers, correspondence, awards and other artefacts, video and audio-tapes, and a large collection of photographs. There is very limited material available before 1975 (when Margaret Thatcher became Leader of the Opposition) and the most significant part of the collection relates to the period when she was Prime Minister 1979-90. The extensive papers in the archive generated after her resignation as Prime Minister mark her activity and influence in the later years of her public life.