Well, there are 2 important clues:
(1) it must come from the lowlands, summer rainfall area; being successful here on the equator
(2) flower opens in the evening
Refering to my handy copy of Mesembs of the World by Gideon Smith, Briza Publisher (1998). Bergeranthus flowers only in late afternoon and close before midnight and is restricted exclusively to the eastern cape near the coast between Port Elizabeth in the west and up to East London and Queenstown. Doing some websearch, the leaf shape and plant habit best matches B. multiceps.