Mundulea sericea or Cork Bush is actually an small tree and a member of the pea family. It seems odd to think that peas also come in tree form but the flowers show that it does. The seeds are also in typical pea-type pods but there are none currently on the tree to take pictures of.
The purple flowers are very attractive against the drab brown of the grassland before the rains turn everything green and the name Cork Bush alludes to the thick corky bark that it has as an adaptation to protect it from fire and frost.
As a member of the pea family, it is also fairly poisonous to fish and the bark is collected, ground up and thrown into water in order to harvest fish. Apparently fish killed in this way are edible if the gills are removed. I'm not sure I'd want to test that, though. The bark contains Roteinoids, which have also been used in commercial insecticides and it has been used as arrow poison, too. all in all it sounds fairly toxic and although it is also used in traditional medicine, this is probably a tree to stay away from.