Sleigh is widely known for his writing and publications dealing with the history of the Cape in South Africa, which are in Afrikaans (with some works translated into English and Dutch).
He went on to work as a physical education teacher in the early 1960s, teaching at Mariental High School in Namibia and the Marist Brothers College in Rondebosch, Cape Town.
[3] In 1969 he completed his BA Degree in History and English Literature at the University of South Africa (UNISA).
This was followed by a series of novels for youth and adults and works of history throughout the 1970s and 1980s, like Tussen twee vlae and Onder die bittervaan.
[4] His 1980 history Jan Kompanjie: Die Wêreld van die Verenigde Oos-Indiese Kompanjie (Jan Compagnie: The World of the Dutch East India Company) formed a key account of the VOC and the Dutch colonial era.