Knock knock, who's there?
1979AD, 11 February, 10 Downing Street, London. Margaret Thatcher arrives at her new official residence and office of British Prime Ministers since 1735.
Margaret Thatcher is the longest-serving Prime Minister of the United Kingdom of the 20th century, having been in office from 1979 to 1990).
She is the only woman ever to have held the post.
Also known as the "Iron Lady", initially a nickname given to her by a Russian journalist, which later became associated with her uncompromising politics and leadership style.
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