Labour's prime minister when Mrs Thatcher became opposition leader on 11 February 1975 was Harold Wilson, who by then had won four general elections, but was to step down a year later, when he was succeeded by James Callaghan.
Now, 50 years after she became leader, the Conservatives once again have a new female leader and Labour is led by a prime minister who won a spectacular general election victory but leads a government rapidly becoming unpopular.
She became leader aged 49, after defeating former prime minister Edward Heath in a shock result in the first ballot, on 4 February, by 130 votes to 119 and then beating William Whitelaw by 146 to 79 in the second ballot a week later.
It was 50 years ago this week that Margaret Thatcher became Conservative Party leader and began to change the course of political history, winning three general elections in the UK and becoming a major figure on the world stage.
On becoming leader, Mrs Thatcher revolutionised Tory thinking, so that when she became PM in 1979 she brought in radical policies never seen before: council house sales, privatisation and a tough crackdown on trade unions.
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