History's forgotten heroes don't get much more radical than the legendary John Brown. Born during the time of the great revolution of the Haitian slaves, he believed he was "an instrument of God", raised up to strike the death blow to American slavery, a "sacred obligation". He attempted to lead a slave revolt when he raided an armoury at Harpers Ferry - an act which help push the country inexorably toward the Civil War. But this was only the final act of a man who had committed his life to the destruction of slavery and an uncompromising hostility to oppression of all kinds.