Since the English and Dutch cultures are relatively open minded and free of prejudice, how did apartheid gain such a foothold in South Africa?

Current politics / times aside…

Throughout most of the 20th century, South Africa was horribly divided by race. I realize that the situation in South Africa was further complicated by the threat of communism (the ANC), and acts of terror from both sides—but most of the white South Africans I have met were actually quite liberal.

England and Holland have been, throughout history, pretty tolerant and open minded havens for all people, even dissident groups, even religious minorities—and are among the most open minded cultures in the world today.

So, why did South Africa, with its English and Dutch background, become so apartheid?

Other English, Dutch, and similar European colonies had similar situations. But South Africa’s racial problems extended into comparatively modern times.