In 1974, in the middle of a Michael Parkinson interview, Muhammad Ali decided to dispense with all the safe conventions of chat show etiquette.

“You say I got white friends,” he declared, “I say they are associates.”

When his host dared to suggest that the boxer’s trainer of 14 years standing, Angelo Dundee, might be a friend, Ali insisted, gruffly: “He is an associate.”

Within seconds, with Parkinson failing to get a word in edgeways, Ali had provided a detailed account of his reasoning.

“Elijah Muhammad,” he told the TV viewers of 1970s Middle England, “Is the one who preached that the white man of America, number one, is the Devil!”

The whites of America, said Ali, had “lynched us, raped us, castrated us, tarred and feathered us … Elijah Muhammad has been preaching that the white man of America – God taught him – is the blue-eyed, blond-headed Devil! No good in him, no justice, he’s gonna be destroyed!

“The white man is the Devil. We do believe that. We know it!”

In one explosive, virtuoso performance, Ali had turned “this little TV show” into an exposition of his beliefs, and the beliefs of “two million five hundred” other followers of the radically – to some white minds, dangerously – black separatist religious movement, the Nation of Islam.

At the height of his tirade, Ali drew slightly nervous laughter from the studio when he told Parkinson “You are too small mentally to tackle me on anything I represent.”

Maybe, though, it was just a judicious sense of self-preservation that prevented Parky from asking arguably the greatest boxer the world has seen to explain how “God” had taught Elijah Muhammad about white Americans being blue-eyed devils.

To explain that, Ali would have had to go back to the 1930s and an obscure door-to-door salesman in Detroit. Wallace D Fard, the founder of the Nation of Islam, appears to have arrived in Detroit in 1930 and began by selling silks to poor black families in the city. His wares, he told his customers, came from “their home country”.

Enough of them were intrigued for Fard to get a following and to be able to switch from the Bible to the Koran as the basis for his preaching.

“My name is W.D. Fard and I came from the Holy City of Mecca,” he supposedly told one early gathering. “More about myself I will not tell you yet, for the time has not yet come.”

It seems that time had still not come when in 1934, Fard mysteriously disappeared. The FBI took the opportunity to creatively fill in the gaps. It told one newspaper that Fard had in fact been a white man from New Zealand, and another that he had been a Turkish-born Nazi agent who had worked for the Germans during World War Two.

Not surprisingly the Nation of Islam has developed a different narrative. Elijah Muhammad, the man who emerged as leader of the Nation of Islam after the “departure” of its founder, came to identify Fard with Allah.

In this scheme of things, Elijah Muhammad, born Elijah Poole, the son of former slaves in Georgia, became the "Last Messenger of Allah."

In a 1996 article that is now on the Nation of Islam’s website, Elijah Muhammad’s wife Tynetta wrote that her husband was chosen as the “Divine Representative” who would preach that the “Master’s” mission had been: “to resurrect His lost and found people, who were identified as the original members of the Tribe of Shabazz from the Lost Nation of Asia. The lost people of the original nation of African descent, were captured, exploited, and dehumanized to serve as servitude slaves of America for over three centuries. “

Elijah Muhammad told the faithful that “the Blackman, the Original Man, [from whom] came all brown, yellow, red and white people,” was to overcome the oppression of whites – the “blue-eyed devils” - and form his own nation.

To some, including the black liberal Supreme Court Justice Thurgood Marshall, the Nation of Islam was “run by a bunch of thugs organised from prisons and jails.”

Others, like the black Conservative commentator George Shuyler may have dismissed Elijah Muhammad as “a rogue and a charlatan” but conceded, in the ugly language of 1950s America, “When anybody can get tens of thousands of Negroes to practice economic solidarity, respect their women, alter their atrocious diet, give up liquor, stop crime, juvenile delinquency and adultery, he is doing more for Negroes' welfare than any current Negro leader I know.”

Muhammad Ali: A life in pictures Show all 20 1 /20 Muhammad Ali: A life in pictures Muhammad Ali: A life in pictures Despite taking his first booking lessons with a local policeman, Clay was simultaneously coached by the more experienced Fred Stoner. Under him, the young boxer won six Kentucky Golden Glove titles, two national Golden Glove titles, and an Amateur Athletic Union National Title. His amateur success culminated when Cassius won the Light Heavyweight gold medal in the 1960 Summer Olympics in Rome. After that, Clay decided to start off his professional career. Getty Images Muhammad Ali: A life in pictures Clay won his first professional fight against Tunney Hunsaker in a six-round decision on October 29, 1960. After that, he went on to establish a record of 19-0 fights, with a total of 15 knockouts. Thanks to his high stature (1.91m), he developed a highly unorthodox style for a heavyweight boxer, relying on foot speed and carrying his hands low rather than on heavy punches. Getty Images Muhammad Ali: A life in pictures By 1963, Clay had not only built a reputation for his boxing technique, but also for correctly predicting the round in which he would "finish" the opponent. Here, he predicts (correctly) the round in which he will knock-out British boxer Henry Cooper. Other boxers Clay defeated prior to his first title fight included Doug Jones, Lamar Clark and Jim Robinson. Getty Images Muhammad Ali: A life in pictures In his first title fight, Cassius Clay opted for world heavyweight champion Sonny Liston. Though few observers thought the 22-year old could defeat an ex-con with ties to organized crime, Clay proved them wrong: in the legendary sixth round of the fight, he landed spectacular combinations of punches, seemingly at will. When Liston told his cornermen he couldn't continue to the seventh round, Clay sprang to the center of the ring, and repeatedly yelled "I’m the greatest!" and "I shook up the world". Cassius Clay had made history for the first time. Getty Images Muhammad Ali: A life in pictures The day after the fight, Cassius Clay announced that he was changing his name to Muhammad Ali for religious reasons. Although he had already been member of Nation of Islam prior to the fight, he was advised not to declare this publicly, in order not to jeopardize his chances. At that time, the Nation of Islam was often viewed with outright suspicion by mainstream America, and Ali did little to counter these impressions: the boxer once stated, for example, that "Integration is wrong. We don't want to live with the white man; that's all." However, after the death of Nation of Islam leader Elijah Muhammad in 1975, Ali converted to mainstream Sunni Islam. Later in his life, he came to embrace spiritual practices of Sufism. Getty Images Muhammad Ali: A life in pictures Muhammad Ali also aroused controversy through his outright opposition to the Vietnam War. When notified of his army classification as 1A in early 1966, the boxer declared that he would refuse to serve, as he considered himself a conscientious objector. He also famously declared about the war: "I ain't got no quarrel with them Viet Cong ... They never called me nigger." When refusing to step forward at his scheduled induction, Ali was arrested and found guilty after a 21-minute trial in June 1967, as a result of which his boxing license was suspended. Refusing to accept the verdict, Ali took the case to the U.S. Supreme Court. In June 1971, with public opinion already against the war, the highest court of the United States reversed his conviction by unanimous decision. Getty Images Muhammad Ali: A life in pictures In 1971, with the case still on appeal, Muhammad Ali was allowed to fight again - in what would become the Fight of the Century against Joe Frazier. It was a heavily promoted fight, with massive popular interest: Frank Sinatra, for example, took pictures for Life magazine. For Ali, it became one of his most crushing defeats. Despite dominating the first third of the fight, he later struggled to keep the pace and, indeed, was put on his back for only the third time in his career. Though he managed to stay on his feet for the rest of round 15, Frazier was declared winner by unanimous decision. In January 1974, however, Ali defeated Smokin' Joe in a non-title rematch. Getty Images Muhammad Ali: A life in pictures In October 1974, Muhammad Ali regained his title in what was to become of the biggest upsets in boxing history. Taking place in Congo, Ali’s fight against champion George Foreman was fittingly promoted as the Rumble in The Jungle. Almost no one gave Ali a chance of winning. Foreman and Ali became friends after the fight, and the movie When We Were Kings, a documentary of the fight in Zaire, even won an Oscar. Getty Images Muhammad Ali: A life in pictures The Thrilla In Manila was Ali's third, an final, fight against Joe Frazier. Leading up to the fight, Ali enraged Frazier through frequent insults and slurs, for example remarking: "It will be a killa ... and a chilla ... and a thrilla ... when I get the gorilla in Manila." It was a tedious fight, with both boxers battling each other into near incapacity. When Frazier's coach refused to allow Frazier to continue, Ali was declared winner by technical knockout. Later on, Muhammad Ali would declare that this was the closest to dying he had ever been, as well as stating that Joe Frazier was "the greatest fighter of all times, next to me." It also inspired the fight scene from Sylvester Stallone's 1976 Oscar-winning film Rocky. Getty Images Muhammad Ali: A life in pictures After the Thrilla In Manila, Ali beat Coopman as well as Jimmy Young and Richard Dunn. Following these wins, he staged an exhibition match with professional wrestler and Mixed Martial Artist Antonio Inoki (picture). This match would seriously jeopardise Ali's health, as both of his legs were bleeding after the fight, leading to an infection. He also suffered two blood cloths in his legs. Getty Images Muhammad Ali: A life in pictures As Ali had briefly lost the heavyweight title to Leon Spinks in February 1978, the Greatest fought a rematch in September, winning the title for a record third time (picture). Even after his retirement, Ali decided to return and win the title for an unprecedented fourth time, but lost against current champion Larry Holmes. As his coach, Angelo Dundee, refused to let Ali come out for the 11th round, it became Ali's only loss by anything other than a decision. Ali also lost his final fight against Trevor Berbick in 1981 by unanimous decision after ten rounds. Getty Images Muhammad Ali: A life in pictures Muhammad Ali is considered to be one of the greatest heavyweights of all time. In total, he won 56 of his 61 fights, 37 by KO. He was also the first person to win the heavyweight title three times. Consequently, he was named Sportsman of the Century by Sports Illustrated as well as Sports Personality of the Century by the BBC. Getty Images Muhammad Ali: A life in pictures Ali became known as a global champion of civil rights, including his friendship with Malcolm X Getty Images Muhammad Ali: A life in pictures His legacy continues to arouse interest up to this day, the most famous example being the biographical film Ali (2002). When Ali found out Will Smith was to play the young boxer, his first reaction was: "You ain't pretty enough to play me." Ali himself published an oral history, entitled Muhammad Ali: His Life and Times, in 1991. Getty Images Muhammad Ali: A life in pictures Muhammad Ali also received a vast number of honours and awards, such as the Spirit of America Award which called him the most recognized American in the world. In 1996, he had the honour of lighting the flame at the 1996 Summer Olympics in Atlanta. For his work with the US civil rights movement and the United Nations, Ali received the Presidential Medal of Freedom as well as the Otto Hahn Peace Medal in Gold. Getty Images Muhammad Ali: A life in pictures Muhammad Ali with his daughters Laila (9 months) and Hanna (2 years 5 months) in London in December 1978 Evening Standard/Getty Muhammad Ali: A life in pictures The boxer has been married four times, with his large family includes seven daughters and two sons. One of his daughters, Laila Ali, has also made herself a name as boxer, despite Ali's early comments against female boxing in 1978: "Women are not made to be hit in the breast, and face like that ... the body's not made to be punched right here. Get hit in the breast ... Hard ... and all that." Getty Images Muhammad Ali: A life in pictures Much of Ali's life after retirement was overshadowed by his suffering from Parkison's Syndrome disease, which was diagnosed in 1984. Nevertheless, he remained a beloved and active public figure right towards the end of his life. He continued to work for humanitarian causes, for example through his appointment as "U.N. messenger of Peace" to Afghanistan in November 2002. During these final years, Ali travelled on average more than 200 days per year. In 2005, he also opened the $50 million non-profit Muhammad Ali Center in Louisville, displaying his boxing memorabilia as well as focussing on core themes of peace, social responsibility, respect and personal growth. Getty Images Muhammad Ali: A life in pictures Muhammad Ali became a goodwill ambassador for the UN, seen here at Kabul airport in November 2002 during a three-day mission Getty Images Muhammad Ali: A life in pictures Muhammad Ali became known for his charity work including the annual Celebrity Fight Night, seen here on April 8, 2016 in Arizona Getty Images

In 1959, the same year that Shuyler was writing, a teenage boxer called Cassisus Clay first heard of the Nation of Islam. He tentatively attended his first meeting in 1961.

And in 1964, the morning after the 22-year-old 7-1 underdog stunned the world by defeating Sonny Liston to become heavyweight champion of the world, he announced that he had renounced his “slave name” Cassius Clay and joined the Nation of Islam.

Beside him as he made his announcement was the man who had become his mentor – Malcolm X.

Malcolm Little had entered a Charlestown jail in 1946 as a hustler convicted of burglary. He had been paroled in 1952 as Malcolm X, a self-educated convert who had ditched his slave name and was burning to go to the Nation of Islam’s Chicago headquarters and meet Elijah Muhammad.

By the time he met Ali in 1962, Malcolm X was Elijah Muhammad’s chief spokesman and most prominent apostle.

His belief that violence was sometimes necessary, and the Nation of Islam’s insistence that followers remain separate from and avoid participation in American politics meant that not every civil rights leader welcomed Muhammad Ali joining the movement.

“When Cassius Clay joined the Black Muslims [The Nation of Islam],” said Martin Luther King, “he became a champion of racial segregation, and that is what we are fighting against.”

The bitter irony is that soon after providing the Nation of Islam with its most famous convert, Malcolm X became disillusioned with the movement. A trip to Mecca exposed him to white Muslims, shattering his belief that whites were inherently evil. He broke from the Nation of Islam and toned down his speeches.

Ali, though, remained faithful to Elijah Muhammad. “Turning my back on Malcolm,” he admitted years later, “Was one of the mistakes that I regret most in my life.”

He was never able to put it right. On February 21 1965 Malcolm X was assassinated as he gave a speech at the Audubon Ballroom in Harlem.

Three members of the Nation of Islam were convicted of the killing. Prosecutors alleged that they had wanted to send a message to Malcolm X’s supporters, but the extent to which they did or did not take orders from above has not been conclusively proved.

Rumours, however, have continued to swirl. In 1993, Louis Farrakhan, by then the Nation of Islam’s new leader, was seen by some to acknowledge the possibility that the movement might somehow have been linked to Malcolm X’s murder when he told a crowd of supporters: “We don't give a damn about no white man law if you attack what we love. And frankly, it ain't none of your business.

“Did you teach Malcolm? Did you put Malcolm out before the world? Was Malcolm your traitor or ours? And if we dealt with him like a nation deals with a traitor, what the hell business is it of yours?”

By then, though, Ali’s own attitudes to the "blue-eyed devils” had long since mellowed. In 1975 he converted to the far more conventional Sunni Islam - possibly prompted by the fact that Elijah Muhammad had died of congestive heart failure in the same year, and his son Warith Deen Mohammad had moved the Nation of Islam towards inclusion in the mainstream Islamic community.

He rebranded the movement the “World Community of Islam in the West”, only for Farrakhan to break away in 1978 and create a new Nation of Islam, which he claimed remained true to the teachings of “the Master” [Fard].

Ali was not among Farrakhan’s followers.

“The Nation of Islam taught that white people were devils,” he wrote in 2004. “I don't believe that now; in fact, I never really believed that. But when I was young, I had seen and heard so many horrible stories about the white man that this made me stop and listen."

The attentive listener to the 1974 interview, might, in fact, have sensed that even then Ali wasn’t entirely convinced about white men being blue-eyed devils.

He had, after all, set the bar pretty high for “associates” like Angelo Dundee to become friends.

“I don’t have one black friend hardly,” he had said. “A friend is one who will not even consider [before] giving his life for you.”