The conquest and retention of Gibraltar was a challenge for Britain in the eighteenth century, not only militarily and diplomatically, but also in the context of domestic politics and culture. Gibraltar was a British imperial possession on the edge of Europe, an imposing but isolated outpost, and the centre of a trade network dominated by Muslim Africans and Sephardic Jews. Its largest ethnic group was Catholic and Genoese. Never well understood by most Britons, Gibraltar became an object of fantasy. The British fantasies are revealing, providing evidence, for example, on popular understandings of Anglo-Muslim relations, the place of Jews within the British empire and Britain's relationship with the European continent. Gibraltar defied easy classification and forced the Britons who commanded there, resided there, or contemplated the outpost from afar to reconsider the importance of Protestantism, European heritage and British identity within the framework of the empire. Before 1748 most British commentary on Gibraltar associated the place with Africans, but after the middle of the century it was increasingly viewed as a bastion defending one frontier of Europe. Following the unsuccessful Spanish siege of 1779-83, Gibraltar became a symbol of British strength and endurance, with Britons standing alone against the rest of the world.