Shirley Vivian Teresa Brittain Williams, Baroness Williams of Crosby, CH, PC was a British politician and academic who represented the Liberal Democrats. Originally a Labour Member of Parliament and Cabinet Minister, she was one of the 'Gang of Four' rebels who founded the Social Democratic Party in 1981. Her career in politics spanned more than 50 years, after she first entered Parliament as the Labour MP for Hitchin in 1964. She retired from political life in 2016, after leading the Liberal Democrats in the House of Lords.