He was an anti-apartheid activist who was tried along with Nelson Mandela and six other men in the 1963-64 Rivonia Trial, and spent 22 years in prison. He joined the African National Congress' (ANC) armed wing to protest the apartheid regime. He and the others were arrested at a secret meeting. He was convicted of sabotage and sentenced to life imprisonment. Being white, he was not sent to the notorious Robben Island prison along with black political prisoners like Mandela. Instead, he was held in Pretoria, most of the time in solitary confinement. He was released in 1985 after agreeing not to take part in political violence. He continued his work against apartheid from exile in London.
