Premise: The Leader of the Conservative Party is the most senior politician within the Conservative Party in the United Kingdom . Margaret Hilda Thatcher , Baroness Thatcher , ( ; 13 October 1925 -- 8 April 2013 ) was a British stateswoman , who served as Prime Minister of the United Kingdom from 1979 to 1990 and as Leader of the Conservative Party from 1975 to 1990 .
Hypothesis: Margaret Thatcher was not the most senior politician within the Conservative Party in the UK.
Label: CONTRADICTION