No proof has been found, but Conservative MP Boris Johnson insists that his ancestor bought himself a wife.
Mr Johnson says his great-great-grandmother, a Circassian slave from a region in southern Russia, was sold to his great-great-grandfather after she fled from war to Turkey in around 1862.
She was set free only when the couple later married.
Yesterday, Mr Johnson insisted he was the "proud offspring of Turkish immigrants", saying: "This is not in any way casting aspersions on my great-great-grandfather.
"He wasn't a slave owner, he was a slave marrier." [Link]