“It was a separation. They, he was not allowed to go through the same door that the — the rest of the party he was with. Obviously, it was apartheid South Africa. There was a white door, there was a black door. He did not want to go through the white door and have the rest of the party go through the black door. He was separated. This was during a trip while they were there in Johannesburg,” campaign manager Kate Bedingfield told reporters.
https://www.nytimes.com/2020/02/26/us/politics/joe-biden-arrest-mandela.html