My understanding and of the Spencer Stanhope scion of Cannon hall, is they have no link whatsoever with the UK Slave and Triangular trade of the 15th,16th,17th and 18th century. My understanding of the other estates within Barnsley, Rockley,Bretton hall, Wentworth Castle and Wodehouse, also had np direct links to this trade either. Oncpme was generated by patronage, marriage, royalty income from mining and rents from tenants including farms. The Fitzwilliam estate did own substantial land in Ireland, which generated a large income. Of course I could be mistaken but having worked at 2 of those estates,I think it would have been mentioned.
Quick check suggests William Spencer Stanhope made money from the iron industry in the late 18th century. Wonder if he made shackles?* *This is an attempt at humour.