Boxing fans love a great comeback story. Muhammad Ali refused to allow himself to be drafted into the US army, in protest against the Vietnam War and racial oppression in the US in 1967.

At the time he was the undefeated heavyweight champion, but as he was plunged into a lengthy legal battle, the various athletic commissions in the country refused to license him to fight and forced him into retirement. But it was his remarkable achievements after his return from exile in the 1970s that made him the most beloved sports figure of his era...