See 12 of the Greatest Photos of Muhammad Ali

Muhammad Ali, who turns 74 on Jan. 17, is best known as one of the greatest heavyweights in the history of boxing. But in his spare time, the People’s Champion enjoyed a pastime rather dissimilar from his athletic pursuits: writing poetry. In 1966, LIFE photographer Gordon Parks spent time with Ali in London, following his winning bout against Henry Cooper. Ali was fighting abroad due to controversies at home: many would-be fans were critical of his involvement with the Nation of Islam and his refusal to serve after being drafted to fight in Vietnam. The Illinois Athletic Commission refused to sanction a fight between him and heavyweight champion Ernie Terrell following statements Ali made saying that the Viet Cong had never shown him any ill will—rather overtly implying that white Americans had.

It was a tense time for Ali. Parks aimed to uncover the man behind the showboating and bravado, a man who had been portrayed by the press as anti-white and a traitor to his country. So the photographer, who also occasionally wrote features for the magazine, began his profile of the boxer with Ali’s reaction to the media maelstrom, written in his own words—and in verse. About the bad press, Ali had this to say:

In honor of Ali’s birthday, here is a collection of LIFE’s greatest portraits of the fighter, from the days when he was known as Cassius Clay to his comeback in the early 1970s.

Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.