Louis Botha, the gentleman on the stocky steed, was the first Prime Minister of the Union of South Africa back in the early 1900s. The Wikipedia article is fairly informative, so let me not repeat all of that here.

From the angle of the photo, and the view of Lion's Head in the background, I'd say there's a fair chance that you worked out that this here is the entrance to Cape Town's parliament buildings, and that the well-known Company's Gargens are more or less to the right of this photo, just behind the parliament buildings.

While thinking about this photos I realised that I've never visited the buildings - and I'm not actually aware whether or not the public can easily gain entrance. Do you perhaps know?