Since time immemorial, royal marriages have had little to do with love - but almost everything to do with diplomacy and dynasty. Clashing personalities have joined in unholy matrimony to form such infamous couples as Russia's Peter II and Catherine the Great and France's Henry II and Catherine de Medici - all with the purpose of begetting a male heir. But with tensions high and silverware flying, kings like England's Henry II fled to the beds of nubile mistresses while Queens such as Eleanor of Aquitaine plotted their revenge.