Forty years ago today, Enoch Powell, member of parliament for Wolverhampton South West, made a speech at Birmingham Conservative Political Centre that was to rock Britain. It also got him sacked from the party and lost him the chance of becoming a future prime minister.

His speech, of which neither a recording nor transcript exists, excited the populace because it referred to "uncontrolled immigration" leading to "rivers of blood" in the streets of Britain. As a Greek classicist, he probably thought it perfectly reasonable to paraphrase Virgil's description of "the River Tiber foaming with much blood" but it went over the heads of most people, and certainly got mangled in its repetition. However, what did come out of his contentious remarks was a greater awareness in Britain of what could happen unless measures were taken to ensure a more equitable and tolerant society - the one to which the British now aspire.