(CNN)-- During much of Nelson Mandela's imprisonment ... His former prison warder Christo Brandt remembers taking 12 birthday cards to Mandela on his 60th birthday. That was his correspondence ...

In the winter of 1964, Nelson Mandela arrived on Robben Island where he would spend 18 of his 27 prison years. Confined to a small cell, the floor his bed, a bucket for a toilet, he was forced to ...