At 80. Not 77. In Basil D’Oliveira: Cricket and Conspiracy Peter Oborne suggests that D’Oliveira may have been the greatest batsman of all time. It is worth remembering that by the age at which Dolly made his test debut, many successful batsmen have retired from the international stage: he did not even play first class cricket till after he had turned 30. Whether or not Oborne is right about that, it is certain that if D’Oliveira had been white then a youtube search would show up footage of him, rather than bringing up an ESPN special about a lesser batsman, in which his name is tagged only because John Vorster preferred having SA expelled from test cricket to having Dolly tour SA with the MCC.
Guardian obit here.
My review of Oborne’s book here. I’ll embed footage of him actually playing if someone can find it. (You can see a little here if you really work at it; in clip 6 the narrator says that John Arlott regarded bringing Dolly to England as the greatest achievement of his life. See this clip of Vorster announcing the cancellation of the tour and make your own judgement).

Oborne has the last word:

Cricket writers often mourn the lost generation of white cricketers such as Graeme Pollock, Mike Proctor or Barry Richards. But at least they got to play some Tests and unrestricted first-class cricket. The penalty that Apartheid inflicted on Eric Petersen, Ben Malamba, Cec Abrahams, Basil D’Oliveira and numerous others was far more absolute. They were denied training, facilities, access to turf wickets and any chance to play for their country at all. Only D’Oliveira escaped to enjoy complete sporting fulfilment, and he got his chance only at the very end of his sporting career, by which time his reflexes had slowed and he was half the brilliant sportsman he had been as a young man in 1950’s South Africa…..It is likely that but for the barbarism of Apartheid D’Oliveira would now be remembered as one of the very greatest cricketers the world has ever seen. By rights he should have imposed his great and singular talent on the cricketing world of the 1950’s, matching himself against the great cricketers of that age: Len Hutton and Denis Compton of England, Everton Weekes, Frank Worrrell and Clive Walcott of the West Indies, Keith Miller and Neil Harvey of Australia.