Roberts is the author of two very good books, on Halifax and Salisbury. His latest work is, in effect, a long essay. His theme is an awkward one, because his two protagonists never saw each other in the flesh, and met only once on the battlefield, at Waterloo. To compare a British general who served the Crown with a French dictator who sought personal domination of Europe is an uneasy task. It is also difficult to find new material in historical territory that has been relentlessly explored for two centuries. Roberts himself seems to recognise this, quoting recognised authorities on the period to support his own assertions.