For me, FKT route would start at Beit Bridge border post - not geographically the northern most place, there are a few farms that are further north, but I think that's the northern-most publicly-accessible starting point, and finish at the cairn that demarcates the southern-most point/meeting of the oceans at Aghullas.
That's the easy bit.
The route is a lot more challenging. Plenty of bikes-banned freeways you will need to avoid, presuming this is a road/gravel bike expedition.
