Lord Denning releases the UK government's official report on the Profumo Affair.

The Profumo sex affair was a major sex scandal in twentieth-century British politics. John Profumo, the Secretary of State for War in Harold Macmillan's Conservative government, had an extramarital affair with 19-year-old model Christine Keeler beginning in 1961. Profumo denied the affair in a statement to the House of Commons, but weeks later a police investigation exposed the truth, proving that Profumo had lied to the House of Commons. The scandal severely damaged the credibility of Macmillan's government, and Macmillan resigned as Prime Minister in October 1963, citing ill health. Ultimately, the fallout contributed to the Conservative government's defeat by the Labour Party in the 1964 general election.

When the Profumo sex affair was first revealed, public interest was heightened by reports that Keeler may have been simultaneously involved with Captain Yevgeny Ivanov, a Soviet naval attach, thereby creating a possible national security risk. Keeler knew both Profumo and Ivanov through her friendship with Stephen Ward, an osteopath and socialite who had taken her under his wing. The exposure of the affair generated rumours of other sex scandals and drew official attention to the activities of Ward, who was charged with a series of immorality offences. Perceiving himself as a scapegoat for the misdeeds of others, Ward took a fatal overdose during the final stages of his trial, which found him guilty of living off the immoral earnings of Keeler and her friend Mandy Rice-Davies.

An inquiry into the Profumo affair by a senior judge, Lord Denning, assisted by a senior civil servant, T. A. Critchley, concluded that there had been no breaches of security arising from the Ivanov connection, although Denning's report was later described as superficial and unsatisfactory. Profumo subsequently worked as a volunteer at Toynbee Hall, an East London charitable trust. By 1975 he had been officially rehabilitated, although he did not return to public life. He died, honoured and respected, in 2006. By contrast, Keeler found it difficult to escape the negative image attached to her by press, law, and parliament throughout the scandal. In various, sometimes contradictory accounts, she challenged Denning's conclusions relating to security issues. Ward's conviction has been described by analysts as an act of establishment revenge, rather than serving justice. In the 2010s the Criminal Cases Review Commission reviewed his case, but ultimately decided against referring it to the Court of Appeal. Dramatisations of the Profumo affair have been shown on stage and screen.

Alfred Thompson "Tom" Denning, Baron Denning, (23 January 1899 – 5 March 1999) was an English lawyer and judge. He was called to the bar of England and Wales in 1923 and became a King's Counsel in 1938. Denning became a judge in 1944 when he was appointed to the Probate, Divorce and Admiralty Division of the High Court of Justice, and transferred to the King's Bench Division in 1945. He was made a Lord Justice of Appeal in 1948 after less than five years in the High Court. He became a Lord of Appeal in Ordinary in 1957 and after five years in the House of Lords returned to the Court of Appeal as Master of the Rolls in 1962, a position he held for twenty years. In retirement he wrote several books and continued to offer opinions on the state of the common law through his writing and his position in the House of Lords.

Margaret Thatcher said that Denning was "probably the greatest English judge of modern times". Mark Garnett and Richard Weight argue that Denning was a conservative Christian who "remained popular with morally conservative Britons who were dismayed at the postwar rise in crime and who, like him, believed that the duties of the individual were being forgotten in the clamour for rights. He had a more punitive than redemptive view of criminal justice, as a result of which he was a vocal supporter of corporal and capital punishment." However, he changed his stance on capital punishment in later life.

Denning was one of the highest profile judges in England because of his report on the Profumo affair. He was known for his bold judgments running counter to the law at the time. During his 38-year career as a judge, he made large changes to the common law, particularly while in the Court of Appeal, and although many of his decisions were overturned by the House of Lords several of them were confirmed by Parliament, which passed statutes in line with his judgments. Although appreciated for his role as "the people's judge" and his support for the individual, Denning was also controversial for his campaign against the common law principle of precedent, and for comments he made regarding the Birmingham Six and Guildford Four, and also as Master of the Rolls for his conflict with the House of Lords.