FWIW, in 1981 and probably many other years the LHR-JNB overnight 747 flight BA051 stopped at Nairobi in the early morning at around 0800 southbound and around midnight northbound.
There were other flights leaving later which also had Nairobi stops including Khartoum ISTR on thursdays.
For many years Nairobi was about as far as they could get without refueling and it was a common stop for the Seychelles etc.