These flowers belong to a pale form of Thunbergia alata. Usually orange, the corolla may also be yellow, even pinkish red, the throat always black inside, unlike the ten other Thunbergia species found in southern Africa, usually pale in the throat. The petal shape is unusual for T. alata, but the black eye reinforces the notion.
The genus comprises about 100 species overall, mainly distributed across tropical Africa and Asia. The photo was taken in the Pretoria National Botanical Garden.