Anthropology.net looks at two 7th-century graves from different parts of England — Kent and Dorset — that prove African-descended people were living in England practically from its start:
In two cemeteries on England’s south coast, archaeologists have found something that rewrites the quiet assumptions about early medieval Britain. Among the graves of the 7th century, nestled between the burials of people with familiar northern European or western British ancestry, lie two individuals whose family stories reached far beyond the North Sea or the Channel. Genetic analysis shows that each had a paternal grandparent from West Africa.
…
Yet in both cases, there is no sign these individuals were treated as outsiders. They were interred according to local customs, suggesting they were accepted and integrated into their communities.
…
One of the most intriguing aspects is that both individuals carried northern European mitochondrial DNA—passed down maternally—paired with autosomal DNA linking them to present-day Yoruba, Mende, Mandenka, and Esan groups. This pattern implies that their fathers, or paternal grandfathers, were of recent West African origin, while their maternal lines were local.
—
You can read more about the genetic archaeology research on these two graves here, in Antiquity.