1979: Thatcher becomes Prime Minister (PA Archive)

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Following a comfortable victory in the 1979 General Election, the Queen asks Margaret Thatcher to form a government, making the Conservative party leader the UK's first (and, so far, only) female Prime Minister. Her tenure at 10 Downing Street earned her the nickname Iron Lady', and she pursued policies based on financial deregulation and mass privatisation and forged a close relationship with US President Ronald Reagan.