Thunbergia neglecta is a perennial that scrambles over other plants and available supports. These flowers were photographed in the Pretoria Botanical Garden.  The growth habit is that of a twiggy branched shrublet (www.sntc.org.sz).  The plant's habitat is partly in the northern provinces of South Africa, but also in Swaziland and Zimbabwe, if not further afield.  This plant does not deserve to be overlooked as the name neglecta might suggest!

(There is a possibility that this may be Thunbergia alata, because of the flower colour and the multiple flowers growing together?)