Somerville College, a constituent college of the University of Oxford in England, was founded in 1879 as Somerville Hall, one of its first two women's colleges. Among its alumnae have been Margaret Thatcher, Indira Gandhi, Dorothy Hodgkin, Iris Murdoch, Vera Brittain and Dorothy L. Sayers. It began admitting men in 1994. Its library is one of Oxford's largest college libraries. The college's liberal tone derives from its founding by social liberals, as Oxford's first non-denominational college for women, unlike the Anglican Lady Margaret Hall, the other to open that year. In 1964, it was among the first to cease locking up at night to stop students staying out late. No gowns are worn at formal halls.