It's simple: the higher-yielding business market does not want to spend all day on an aircraft. Especially when there's no real time difference between ZA and the UK, so you can work in Johannesburg (or wherever) all day, get on board and get a full night's sleep, and work all the next day in London.

Indeed, quite a lot of the leisure market would also not want to spend an entire day of their holiday sitting on an aircraft, for similar reasons - one more day of holiday entitlement that has to be used, and it's not exactly a barrel of laughs sitting in an economy seat all day.

We always have to remember that the proportion of passengers who fly for any reason other than to get from A to B, with the flight being a necessary evil to do so, is very small.