In 1967, the world heavyweight champion, Muhammad Ali, refused to be indicted into the American military. His decision to follow his conscience and not serve in Vietnam galvanised radicals across the US.

Simon Watts speaks to Dr Nathan Hare about a visit by Muhammad Ali to Howard University at the height of the outcry over his refusal of the draft.

(Photo: Muhammad Ali in training. Credit: R McPhedran/Express/Getty Images)