Tony Blair has led tributes to the former Conservative minister John Profumo, who has died aged 91.
Mr Profumo resigned as war secretary in 1963 after lying to MPs about his affair with call girl Christine Keeler.
Mr Profumo, who died two days after having a stroke, went on to work for an east London charity for 40 years.
The prime minister said Mr Profumo had made a "serious mistake" but "underwent a journey of redemption" and "gave support and help to many, many people".
Mr Profumo died during Thursday night, while surrounded by his family, at London's Chelsea and Westminster Hospital.
During what became known as the Profumo Affair, which happened at the height of the Cold War, it emerged Ms Keeler had also been involved with Commander Yevgeny Ivanov, a Soviet intelligence officer and assistant naval attache in London.
THE PROFUMO AFFAIR
Sleaze A picture of Christine Keeler, naked on a chair, became an image of the era.
Sex parties Ms Keeler lived with Stephen Ward at his flat, where he threw parties for the high-ranking and influential.
Soviet spy Christine Keeler had a fling with Mr Profumo, and had had relations with a Soviet intelligence officer.
Lies When the affair came to light in March 1963, John Profumo initially tried to deny it. Ten weeks later he told MPs he had misled them, and quit.
Government Prime Minister Harold Macmillan stepped down in October 1963 through ill-health, said to be made worse by the Profumo Affair. In 1964 the Tories lost to Labour.
Warheads Christine Keeler later claimed Ward was a Soviet spy and had asked her to get information from Mr Profumo about nuclear warheads in West Germany.
Within days of quitting politics, Mr Profumo walked into Toynbee Hall, an east London charity, and asked to help with the washing up.
More than 40 years later he was still working for the charity, with which he had stints as chairman and president.
His friend Lord Deedes told the BBC: "The fact is what he did, and continued to do until quite recently, [was] a very long stint of social work for the poor of east London.
"And if that isn't considered to be sufficient atonement for the mistake he made, then there's no such thing as forgiveness."
Former Conservative leader Iain Duncan Smith also said he would remember Mr Profumo for his "remarkable work" in east London.
Mr Profumo, a charming and respected Tory politician who was educated at Harrow and Oxford, had been the rising star of Harold Macmillan's Conservative government.
He entered the Commons in 1940 aged 25, and in July 1960 was made Secretary of State for War.
His brief affair with Ms Keeler began after he was introduced to her by fashionable London osteopath and artist Stephen Ward, at Lord Astor's Cliveden country estate, in Berkshire, in July 1961.
In an interview in 1989 she described Mr Profumo as "a lot of fun".
"But he was too old for me. I really just went out with him because I was impressed with who he was," she said.
In March 1963, Mr Profumo, who was married to the actress Valerie Hobson, made a statement to MPs denying any impropriety in his relationship with Ms Keeler.
He resigned three months later after admitting he had misled the House of Commons.
The Profumo Affair was one of the most sensational political scandals of the 20th Century and was later dramatised in a film starring Sir Ian McKellen as Mr Profumo.
Mr Ward - infamous for his sex parties involving the rich and influential - was later prosecuted for living on immoral earnings.
He committed suicide on the last day of the trial before the jury reached its verdict.
Ms Keeler was found convicted on unrelated charges - for not attending as a witness in the trial of a man shot at her home - and sentenced to nine months in Holloway Prison.
Award for work
While working for Toynbee Hall, Mr Profumo used his political skills to raise huge funds, and expanded the charity's activities to include social programmes and youth training.
His wife also gave her time to helping others, working until her death in 1998 for the leprosy charity Lepra.
Mr Profumo was awarded the CBE in 1975.
In 1995 Margaret Thatcher, who called him "one of our national heroes", invited him to her 70th birthday dinner, and seated him next to the Queen.
Lady Thatcher said then: "It's time to forget the Keeler business. His has been a very good life."