The UK’s new visa scheme for top global graduates, which does not include those from African universities, is “de facto” exclusionary and is “retrograde” and “self-limiting” a professor at the University of the Witwatersrand in Johannesburg has told the BBC’s Newsday programme.

The university rankings are “imperfect”, said Prof Lynn Morris, the deputy vice-chancellor of research and innovation at the university.

Alumni of the top non-UK universities who graduated in the past five years will be eligible.

To qualify, a person must have attended an institution that appeared in the top 50 of at least two of the Times Higher Education World University Rankings, the Quacquarelli Symonds World University Rankings, or The Academic Ranking of World Universities in the year they graduated.

Thirty-seven universities have made the list - most are in the US, but there are also some in Europe and Asia, none are in Africa.

“The ranking system I think is really not the right way to be choosing the best people,” Prof Morris said, "highlighting that each ranking has different universities on their lists."

She said people from “the global south” approach problems in different ways to the northern hemisphere, and this is something that should be tapped into to encourage “equity and diversity”.

She also highlighted the strengths of South African science when it came to tracking Covid and in “helping the world develop vaccines”.