Having helped their businessmen develop the trade, the British government made slavery illegal, ensuring that there was never a slave population in Britain, as there was in America. They exported the racial friction, resentment and paranoia that ought to have been the country’s legacy and punishment for the slavers’ crimes. It’s yet another glaring injustice of the whole business.
Most British people didn’t have to deal with the consequences of colonialism until the British government started to invite immigration from former dependencies to ease labour shortages. Even now, people of colour still make up a much smaller proportion of the total population in the UK, compared to the USA. The 2020 American census has the “non-Latino” white population at 57.8%, and the Black population at 12.1. In the UK, the 2019 estimates were that the white people amounted to around 84.8% of the population, whereas Black people made up 3.5%, according to the Government website GOV.UK.
In the US, emancipation led to around 4 million virtually destitute ex-slaves making up a large proportion of the population, especially in the south, where most had been employed, usually in agriculture. The savage and immediate memory of enslavement led to suspicion, prejudice and discrimination, division and violence as black people remembered all too well the cruelty with which they had been treated, and their paranoid former masters feared the righteous anger of such a large number of people. Ironically, this fear of black violence has led to most acts of racial violence being committed by white people against people of colour (I believe). White people are much more of a threat to Black people than vice versa.
British mistreatment of people of colour has always had a different character to that of The United States. Often, it has been manifest as racist outrages and offences by particular racist individuals, a response to the perceived threats of immigration, and has been driven by xenophobic suspicion, bigotry, and nationalist arrogance. In other words, it has tended to be the result of personal prejudice and antipathy (although that is culturally incubated) and has never been so explicitly and systematically encoded in British institutions, laws and procedures.
Instead, a whole set of related factors has led to inequality of opportunity and of social outcome in our society. This has been far more likely to disadvantage people from ethnic minority immigrant demographics. This may foster certain expectations about people from those groups, but the great irony and injustice of the situation is that a society such as ours can be racially unfair without any individual person holding any racist beliefs at all.
The source of racial injustice is our shoulder-shrugging, “What-Can-You-Do?”, “I’m-alright-Jack” acceptance of the principle that inequality is natural and inevitable. Deal with that, create a truly egalitarian society, and you start to deal with British racism.