BA in J AMS-LHR-JNB €1.630,- & CPT €1.760,-
Wide open in 2018 - also during (Dutch) school holidays.
I believe this is a very good deal for this route!
Please check:
JNB
https://goo.gl/flights/ek7b
CPT
https://goo.gl/flights/APir
BTW: In Y it's €420,- to JNB. But books in O or Q.