Just got bused past a parked BA A380 at JNB, after coming in on a B747. Both of which (along with a fair few other European carriers) seem to spend their day dozing in the South African winter sun.

Considering BA never leaves any money on the table, why would BA not get these birds to work for a day rotation back to London?

I would guess part of the answer is that most people will prefer the night flight, but surely that is not reason enough to just let these birds idle away for a full day?