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What brought about Margaret Thatcher's downfall?

9 April 2013 Last updated at 12:08 BST

Baroness Thatcher, Britain's first female premier, was Conservative prime minister from 1979 to 1990 and won three successive general elections.

She has died "peacefully" after suffering a stroke while staying at the Ritz hotel in central London.

In the third of four Newsnight films, Martha Kearney considers what brought an end to Margaret Thatcher's political career - not the unions or the opposition or the electorate, but the Conservative politicians closest to her.