//By the mid 18th century London had the largest Black population in Britain, made up of free and enslaved people, as well as many runaways. The total number may have been about 10,000.[28]
It was regarded as fashionable amongst the upper classes to have a Black servant and they sometimes feature in paintings, such as 'The family of Sir William Young' by Zoffany. There were Black people in many other towns, such as Liverpool, Bristol, Bath and Lancaster. Smaller number of Black people were also found in rural areas throughout the country.
A number of Black people achieved prominence. Ignatius Sancho (1729–1780) opened his own grocer's shop in Westminster. He wrote poetry and music and his friends included the novelist Laurence Sterne, David Garrick the actor and the Duke and Duchess of Montague. He is best known for his letters which were published after his death. Others such as Olaudah Equiano and Cuguano were active in the abolition campaigns.
The legal status of enslaved people in Europe was often unclear. In Britain it was not finally resolved until abolition in 1838, though after the famous Somerset case in 1772 enslaved people could not be sent back to the colonies against their will.[28]//
From Mikey's link, this section...
https://en.wikipedia.org/wiki/Slavery_in_the_British_Isles#Enslaved_Africans