Was Margaret Thatcher The Longest Serving British Prime Minister?

Margaret Thatcher was born on October 13th 1925 and was Prime Minister of Britain from 1979 ~ 1990. She was the longest-serving British Prime Minister since William Ewart Gladstone, who served as PM for 26 years. Not only did Mrs Thatcher serve for an incredible 11 years, she also had the longest continuous period in office since Lord Liverpool in the early nineteenth century. She is also the only woman to have served as Prime Minister or as leader of a major political party in the UK, and along with Margaret Beckett, is one of only two women to hold any of the four great offices of state. Undoubtedly one of the most significant British politicians in recent political history, she has attracted both strong support and strong opposition form the British public. Margaret was born Margaret Hilda Roberts and began her life in the town of Grantham in Lincolnshire. Her father, Alfred Roberts was not only a local greengrocer but very active in local politics, so maybe this is where she got her own passion for politics from.

No.  Tony Blair served longer.