Powell made the speech at the Midland Hotel in Birmingham to a meeting of the Conservative Political Centre at 2:30 pm. The Birmingham-based television company ATV saw an advance copy of the speech the morning it was delivered, and its news editor ordered a television crew to go to the venue, where they filmed sections of the speech. Earlier in the week, Powell said to his friend Clement Jones, who was a journalist at the Wolverhampton Express & Star, "I'm going to make a speech at the weekend and it's going to go up 'fizz' like a rocket; but whereas all rockets fall to the earth, this one is going to stay up".
The title given to the speech arose from its allusion to Virgil's line from the Aeneid 6, 86, in which the Sibyl prophesies "wars, terrible wars, and the Tiber foaming with much blood" (Bella, horrida bella, Et Thybrim multo spumantem sanguine).
Powell recounted a conversation with one of his constituents, a middle-aged working man, a few weeks earlier. Powell said that man told him: "If I had the money to go, I wouldn't stay in this country... I have three children, all of them been through grammar school and two of them married now, with family. I shan't be satisfied till I have seen them all settled overseas." The man finished by saying to Powell: "In this country in 15 or 20 years time the black man will have the whip hand over the white man. Powell went on:
Here is a decent, ordinary fellow-Englishman, who in broad daylight in my own town says to me, his Member of Parliament, that the country will not be worth living in for his children. I simply do not have the right to shrug my shoulders and think about something else. What he is saying, thousands and hundreds of thousands are saying and thinking – not throughout Great Britain, perhaps, but in the areas that are already undergoing the total transformation to which there is no parallel in a thousand years of English history.
Powell quoted the Registrar-General's statistics that in 15 to 20 years, there would be 3.5 million immigrants and their descendants in Britain. Powell estimated that by the year 2000, the figure would be 5 to 7 million, around one tenth of the population. Powell claimed that it was urgent to stop "further inflow, and by promoting the maximum outflow" because by 1985, the majority of the immigrant community would have been born in Britain. Powell asserted that this was "part of the official policy of the Conservative Party". He went on to say:
We must be mad, literally mad, as a nation to be permitting the annual inflow of some 50,000 dependants, who are for the most part the material of the future growth of the immigrant descended population. It is like watching a nation busily engaged in heaping up its own funeral pyre. So insane are we that we actually permit unmarried persons to immigrate for the purpose of founding a family with spouses and fiancées whom they have never seen.
He advocated voluntary re-emigration by "generous grants and assistance" and he claimed that immigrants had asked him whether it was possible. Powell said that all citizens should be equal before the law, and that:
This does not mean that the immigrant and his descendants should be elevated into a privileged or special class or that the citizen should be denied his right to discriminate in the management of his own affairs between one fellow-citizen and another or that he should be subjected to an inquisition as to his reasons and motives for behaving in one lawful manner rather than another.
He argued that journalists who urged the government to pass anti-discrimination laws were "of the same kidney and sometimes on the same newspapers which year after year in the 1930s tried to blind this country to the rising peril which confronted it." Powell said that such legislation would be used to discriminate against the indigenous population and that it would be like "throwing a match on to gunpowder. Powell described what he thought the position of the indigenous population would be:
For reasons which they could not comprehend, and in pursuance of a decision by default, on which they were never consulted, they found themselves made strangers in their own country. They found their wives unable to obtain hospital beds in childbirth, their children unable to obtain school places, their homes and neighbourhoods changed beyond recognition, their plans and prospects for the future defeated; at work they found that employers hesitated to apply to the immigrant worker the standards of discipline and competence required of the native-born worker; they began to hear, as time went by, more and more voices which told them that they were now the unwanted. On top of this, they now learn that a one-way privilege is to be established by Act of Parliament; a law which cannot, and is not intended to, operate to protect them or redress their grievances, is to be enacted to give the stranger, the disgruntled and the agent provocateur the power to pillory them for their private actions.
Powell quoted a letter he received from a woman in Northumberland, about an elderly woman living in a Wolverhampton street where she was the only white resident. The elderly woman had lost her husband and her two sons in World War II and had rented out the rooms in her house. Once immigrants had moved into the street she was living in, her white lodgers left. Two black men had knocked on her door at 7 am to use her telephone, but she refused and was verbally abused. She had asked her local authority for a rates reduction, but was told by a council officer to let out the rooms of her house. When the woman said the only tenants would be black, the council officer replied: "Racial prejudice won't get you anywhere in this country." The next part of the letter that Powell quoted went:
She is becoming afraid to go out. Windows are broken. She finds excreta pushed through her letterbox. When she goes to the shops, she is followed by children, charming, wide-grinning piccaninnies. They cannot speak English, but one word they know. "Racialist", they chant. When the new Race Relations bill is passed, this woman is convinced she will go to prison. And is she so wrong? I begin to wonder.
Powell argued that although "many thousands" of immigrants wanted to integrate, he contended that the majority did not, and that some had vested interests in fostering racial and religious differences "with a view to the exercise of actual domination, first over fellow-immigrants and then over the rest of the population". Powell's peroration of the speech gave rise to its popular title. He quotes the Sibyl speaking in the epic poem Aeneid:
As I look ahead, I am filled with foreboding. Like the Roman, I seem to see "the River Tiber foaming with much blood". That tragic and intractable phenomenon which we watch with horror on the other side of the Atlantic but which there is interwoven with the history and existence of the States itself, is coming upon us here by our own volition and our own neglect. Indeed, it has all but come. In numerical terms, it will be of American proportions long before the end of the century. Only resolute and urgent action will avert it even now. Whether there will be the public will to demand and obtain that action, I do not know. All I know is that to see, and not to speak, would be the great betrayal.
According to C. Howard Wheeldon, who was present at the meeting where Powell gave the speech, "it is fascinating to note what little hostility emerged from the audience. To the best of my memory, only one person voiced any sign of annoyance. The day after the speech Powell went to Sunday Communion at his local church and when he emerged there was a crowd of journalists and a local plasterer (Sidney Miller) said to Powell: "Well done, sir! It needed to be said. Powell asked the assembled journalists: "Have I really caused such a furore?" At midday Powell went on the BBC's World This Weekend to defend his speech and he appeared later that day on ITN news.
The Labour MP Edward Leadbitter said he would refer the speech to the Director of Public Prosecutions. The Liberal Party leader Jeremy Thorpe spoke of a prima facie case against Powell for incitement. Baroness Gaitskell called the speech "cowardly" and the cricketer Sir Learie Constantine condemned it.
The leading Conservatives in the Shadow Cabinet were outraged by the speech. Iain Macleod, Edward Boyle, Quintin Hogg and Robert Carr all threatened to resign from the front bench unless Powell was sacked. Margaret Thatcher thought that although some of Powell's speech was "strong meat" she sympathised with his overall message and said to Heath when he telephoned her to inform her Powell was to be sacked: "I really thought that it was better to let things cool down for the present rather than heighten the crisis." The Conservative leader, Edward Heath, sacked Powell from his post as Shadow Defence Secretary, telling him on the telephone that Sunday evening (it was the last conversation they would have). Heath said of the speech in public that it was "racialist in tone and liable to exacerbate racial tensions". Conservative MPs on the right of the party—Duncan Sandys, Gerald Nabarro, Teddy Taylor—spoke against Powell's sacking. On Monday, 22 April Heath went on Panorama, telling Robin Day: "I dismissed Mr. Powell because I believed his speech was inflammatory and liable to damage race relations. I am determined to do everything I can to prevent racial problems developing into civil strife... I don't believe the great majority of the British people share Mr. Powell's way of putting his views in his speech."
On 23 April, 1,000 dockers went on strike in protest at Powell's sacking and marched from the East End to the Palace of Westminster carrying placards saying "Don't knock Enoch" and "Back Britain, not Black Britain". 300 of them went into the Palace, 100 to lobby the MP for Stepney, Peter Shore, and 200 to lobby the MP for Poplar, Ian Mikardo. Shore and Mikardo were shouted down and some dockers kicked Mikardo. Baroness Gaitskell shouted: "You will have your remedy at the next election." The dockers replied: "We won't forget. The organiser of the strike, Harry Pearman, headed a delegation to meet Powell and said after: "I have just met Enoch Powell and it made me feel proud to be an Englishman. He told me that he felt that if this matter was swept under the rug he would lift the rug and do the same again. We are representatives of the working man. We are not racialists. On 24 April 600 dockers at St Katharine's Docks voted to strike and numerous smaller factories across the country followed. 600 Smithfield meat porters struck and marched to Westminster and handed Powell a 92-page petition supporting him. Powell advised against strike action and asked them to write to Harold Wilson, Heath or their MP. However, strikes continued, reaching Tilbury by 25 April and he received his 30,000th letter supporting him, with 30 protesting against his speech. By 27 April 4,500 dockers were on strike. On 28 April, 1,500 people marched to Downing Street chanting "Arrest Enoch Powell". Powell received 43,000 letters and 700 telegrams supporting him by early May, with 800 letters and four telegrams against. On 2 May the Attorney-General, Sir Elwyn Jones, announced he would not prosecute Powell after consulting the Director of Public Prosecutions.
The Gallup Organization took an opinion poll at the end of April and found that 74% agreed with what Powell had said in his speech; 15% disagreed. 69% felt Heath was wrong to sack Powell and 20% believed Heath was right. Before his speech Powell was favoured to replace Heath as Conservative leader by 1%, with Reginald Maudling favoured by 20%; after his speech 24% favoured Powell and 18% Maudling. 83% now felt immigration should be restricted (75% before the speech) and 65% favoured anti-discrimination legislation.
Powell defended his speech on 4 May through an interview for the Birmingham Post: "What I would take 'racialist' to mean is a person who believes in the inherent inferiority of one race of mankind to another, and who acts and speaks in that belief. So the answer to the question of whether I am a racialist is 'no'—unless, perhaps, it is to be a racialist in reverse. I regard many of the peoples in India as being superior in many respects—intellectually, for example, and in other respects—to Europeans. Perhaps that is over-correcting.
After Powell delivered the speech, there were attempts to locate the constituent whom Powell described as being victimised by non-white residents. Despite combing the electoral register and other sources, the editor of the Wolverhampton newspaper, Clem Jones (a close friend of Powell, who broke off relations with him over the controversy), and his journalists failed to identify the woman. Powell refused to name her because he felt he had to respect her confidentiality, even to the point of withdrawing from a libel action against a national newspaper.
Shortly after Powell's death, Kenneth Nock, a Wolverhampton solicitor, wrote to the Express and Star in April 1998 to claim that his firm had acted for the woman in question, but that he could not name her due to rules concerning client confidentiality. In January 2007, the BBC Radio Four programme Document, followed by the Daily Mail, claimed to have uncovered the lady. They said she was Druscilla Cotterill (1907–1978), the widow of a Battery Quartermaster Sergeant with the Royal Artillery who was killed in World War II. She lived in Brighton Place in Wolverhampton, which by the 1960s was dominated by immigrant families. In order to increase her income, she rented rooms to lodgers, but did not wish to rent rooms to West Indians and stopped taking in any lodgers when the Race Relations Act 1968 banned racial discrimination in housing. She locked up the spare rooms and lived only in two rooms of the house. According to those who remember the period, the many children in the street regarded her as a figure of fun, and taunted her. The Radio 4 programme which claimed the woman was Mrs Cotterill did, however, note that she did not match all the characteristics of the woman mentioned by Powell in the speech. For example, Mrs Cotterill had no sons and no telephone.
In the United Kingdom, particularly in England, "Enoch was right" is a phrase of political rhetoric, employed by the far right, inviting comparison of aspects of contemporary English society with the predictions made by Powell in the Rivers of Blood speech. The phrase implies criticism of racial quotas, immigration and multiculturalism. "Enoch was right" badges were available in the United Kingdom at one point, as were stickers bearing the slogan "Come back Enoch Powell – we should have listened". Following the St Pauls, Bristol, Brixton, Toxteth and Handsworth riots in the 1980s, Powell claimed that his "rivers of blood" prediction had come true.
In November 2007, Nigel Hastilow resigned as Conservative candidate for Halesowen and Rowley Regis after he wrote an article in the Wolverhampton Express & Star that included the statement: "Enoch, once MP for Wolverhampton South-West, was sacked from the Conservative front bench and marginalised politically for his 1968 'rivers of blood' speech, warning that uncontrolled immigration would change Britain irrevocably. He was right and immigration has changed the face of Britain dramatically".