I’m just interested in the progression of black rights in Britain compared to the US
I answered the first of these questions here. Essentially, slavery became outlawed when it was no longer profitable; this political and economic calculation was underwritten by antislavery advocates and middle-class abolitionists who had come to see slavery as deeply morally suspect.
To answer the second question, the British Empire always maintained the line that all British subjects in the British Commonwealth were members of a community of equals and allowed the same rights. In fact, Britain's early abolition of slavery became an important rhetorical flank in this argument—it proved that Britain was always on the moral "cutting edge."
In 1948, Parliament passed the British Nationality Act, giving all British subjects the unrestricted right of entry into the UK—making Britain's benevolent self-narrative legal reality. But despite these gestures and laws, Parliament, and white British society in general, was never able, comfortable, or willing to actually follow through on the implications of its own rhetoric: that the black British subjects who had right of entry into the UK would actually take Britain up on it, and that these black Britons would actually expect Britain to make good on its promise of equality and community and to treat them as equals. Thus, the main core of the black civil rights movement in Britain, particularly after 1948, was that black Britons asked, demanded, and fought for, as the historian Kennetta Hammond Perry has written, their right to belong and their right to be seen as British citizens and accorded the rights promised to them.
Two examples, both from Kennetta Perry's book London is the Place for Me, help highlight this point:
While much of the news of the day, and scholarship since, has focused on the outbreak of race riots (which did happen and British popular responses to those riots could be another post on its own), black Britons also responded to other acts of violence against black migrants in ways that forced white British society to consider their demands and take them seriously. Consider the case of Antiguan-born Kelso Cochrane, who was stabbed by six white men in May of 1959. The police concluded that the case was simply an unfortunate robbery, but the black activist community in Britain (which had its roots in the 1930s and potentially even earlier) and its associated organizations and periodicals (e.g., the Committee of African Organizations, the West Indian Gazette* newspaper) disagreed and made their disagreement known. They compared Cochrane's murder to other instances of racially-motivated murder in America; invoking Jim Crow in this way was a direct challenge to Britain's long-standing self-narrative that Britain "didn't have a race problem." They campaigned, organized, held a public funeral, and essentially took action to make sure that the murder was understood as a raced, political event, that "embodi[ed] the problem of racism and racism and, more specifically, Blackness in Britain" (HP, 129).
Legally: A big moment in the history of race relations in Britain is the passage of the Commonwealth Immigrants Act 1962. The act actually rolled back the "unrestricted right of entry" provision granted by the British Nationality Act. As the historian Kathleen Paul has argued, the act emerged out of British policymakers' unwillingness to deal with race or to imagine a diverse future for Britain.
But black Britons took action to lobby against the bill, and engaged in new forms of organizing and coalition-building to do so. In the pages of the West Indian Gazette, black activists laid out their arguments not only against Parliament's machinations but also their arguments for the importance, vibrancy, and urgency of the black British community. And again, their arguments invoked the struggles of other ethnic groups within Britain as well as in America—showing that the black civil rights movement was always engaged in wider forms of transnational social justice activism. Perry argues that, while the BNA was indeed rolled back and replaced with the much more restrictive Commonwealth Immigrants Act in 1962, this work made race relations a "wedge issue" (HP, 185) and indeed helped accelerated the entry of "race relations" into the public consciousness in the 1960s.
However, there were limits to what this activism could do, especially as the 1960s progressed. The passage of the 1965 Race Relations Act—so soon after a punitive migration bill—was a triumph in that it placed racial discrimination at the center of policymaking. Yet it was also a limited bill that could not, on its own, change race relations in Britain wholesale. Really, I think a main takeaway of Perry's argument is that even where activists were not successful in the ways we think of the term, or where their coalitions and organizations broke down, they succeeded in forcing white Britons to rethink the idea that Britain "didn't have a race problem," and in making the state pay attention to them as citizens who had rights.
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