The care that David Richardson took, both in titling and in sub-titling his new book on Britain's transatlantic slave trade, is quite evident. This is not just a book on the abolition of Britain's slave trade, with a bit of material on Britain's previous conduct of its slave trade as a more or less unconnected prologue. This is a book about both things—“the British slave trade” and also “its abolition”—and it takes seriously the idea that the way in which the slave trade was ended had everything to do with how it had been conducted. And Richardson's presentation of both things bears out the double meaning of “principles/principals” in the before-the-colon title. The conduct of the slave trade, in his view, largely was an attempt to manage this particular manifestation of the classic “principal-agent” problem. Abolition, similarly, was a matter of principle, but the various sets of agents that carried it out related to that principle in diverse ways. Where Richardson shows these motivations for the political movement that eventually secured the Abolition Act in 1807, Mary Wills does so for the naval officers tasked with interdicting the transatlantic slave trade after that date, and Maeve Ryan does for the often self-interested agents of the Crown whose business was to resettle the Africans on captured slave ships within the bounds of the British Empire.