Abstract:This essay, first presented as a 2009 conference paper on comparative British/Spanish history in the eighteenth century, was written in 2012 and has been revised/updated in 2019. Imperial histories have often been interpreted as cycles of rise and fall; or, alternatively, as linear tales of progress. Neither the British nor the Spanish experiences fitted into such neat models of historical change. The discussion explores their case histories, and considers also many other empires-some dramatically short-lived, others showing great longevity. Instead, the British and Spanish empires exemplified trends of growth/collapse, which were crosscut with the ballasting forces of continuity. They sprang from specific circumstances and global powerimbalances; and they then became operational factors in their own right, proving both long-lasting and historically influential. It is not satisfactory therefore to interpret their histories as purely framed by accident and contingency. The balance of power and resistance to power with and outside these global empires was crucial-as well as the framing context of changing social attitudes to empire and nationhood. History is not a tale of randomised chaos but one of organised complexity.