 Williams was Member of Parliament (MP) for Hammersmith South from a 1949 by-election to 1955, Baron's Court from 1955 to 1959, and Warrington from a 1961 by-election.Williams served as parliamentary private secretary to the Attorney-General from 1964.In 1969, Williams was appointed by the then-East Pakistan based Awami League, one of Bangladesh's main political factions since independence in 1971, to represent Pakistani and later-Bangladeshi politician Sheikh Mujibur Rahman in the Agartala Conspiracy Case.