On a freezing winter's night, a few hours before dawn on May 12, 1969, South African security police stormed the Soweto home of Winnie Madikizela-Mandela, activist and wife of the imprisoned Nelson Mandela, and arrested her in the presence of her two young daughters, then aged nine and ten. Rounded up in a group of other antiapartheid activists under Section 6 of the Terrorism Act, designed for the security police to hold and interrogate...