Complex sentence: It was the first agreement in apartheid South Africa by acknowledged black and white political leaders in South Africa that subscribed to such principles, which would ultimately end with the negotiations between President F.W. de Klerk and Nelson Mandela in 1993.
Split into simpler sentences: It was the first agreement in apartheid South Africa by acknowledged black and white political leaders that subscribed to such principles. Final negotiations were ultimately conducted between between President F.W. de Klerk and Nelson Mandela in 1993.