The "Rivers of Blood" speech was made by British Member of Parliament (MP) Enoch Powell on 20 April 1968, to a meeting of the Conservative Political Centre in Birmingham, England. His speech made various remarks, which included strong criticism of significant Commonwealth immigration to the United Kingdom and the proposed Race Relations Act, which made it illegal to refuse housing, employment, or public services to a person on the grounds of colour, race, ethnic or national origins in the country. It became known as the "Rivers of Blood" speech, although Powell always referred to it as "the Birmingham speech". The former name alludes to a prophecy from Virgil's Aeneid which Powell, a former classical scholar, quoted:As I look ahead, I am filled with foreboding; like the Roman, I seem to see 'the River Tiber foaming with much blood'.

Harold Wilson was appointed Prime Minister of the United Kingdom by Queen Elizabeth II on 16 October 1964 and formed the first Wilson ministry, a Labour government, which held office with a thin majority between 1964 and 1966. In an attempt to gain a workable majority in the House of Commons, Wilson called a new election for 31 March 1966, after which he formed the second Wilson ministry, a government which held office for four years until 1970.