The history of British slave ownership has been buried: now its scale can be revealed

  I think that is the main reason why its not the same running sore as in the US as black slaves and their descendants were rare in Britain itself. At least unless you got the movement of people from the Caribbean to Britain, a century after the end of slavery.  Before then the coloured element of the population was very small and most would not have been slaves probably.  However I think the primary source of ignorance about the scale of the slaver trade in Britain is simply the poor education in history at schools and lack of interest in general.  There is plenty of information out there including on TV and other electronic media. 

  Interesting that so many fairly moderately wealthy people seem to have had a share in actual ownership of slaves.  Had always thought it was mainly the rich planters and shipowners so that was illuminating.  Given those numbers and the way gene pools have spread I suspect many people in western Europe probably have at least one ancestor who was either an owner or trader at some stage.   This will also include many people who's origins were beyond the region as until the reaction against slavery that started in western Europe it was an almost universal activity.  [Although generally not as bad I believe as what happened to black slaves taken from Africa by European and Muslim traders/raiders.]

  Steve