The world’s best-known espionage officer, Vladimir Putin, would relish Christopher Andrew’s account of the role of his fellow practitioners at the 1816 Congress of Vienna. The secret services of France, Prussia, Britain, Russia, and Austria jostled to monitor the trysts of courtesans with the statesmen assembled in the Austro-Hungarian capital to carve post-Napoleonic Europe into spheres of influence. In some cases, these delicate sources were bestowing favours serially. More than one secret service was gleaning the pillow talk. The Russian Princess Catherine Bagration, mother of Austrian Foreign Minister Klemens von Metternich’s illegitimate daughter, was receiving at least two, including Tsar Alexander I. Metternich’s then current mistress, the Duchess of Sagan, entertained, separately, two British diplomats, including the British Ambassador to Vienna. How piquant, that Metternich deployed his own agents to keep abreast of the duchess’s other liaisons.