From 1827 to 1843, the United Kingdom had a base on Bioko to suppress the transatlantic slave trade, which was then moved to Sierra Leone upon agreement with Spain in 1843. In 1844, on restoration of Spanish sovereignty, it became known as the "Territorios Españoles del Golfo de Guinea". Spain had neglected to occupy the large area in the Bight of Biafra to which it had treaty rights, and the French had been expanding their occupation at the expense of the area claimed by Spain. The Treaty of Paris in 1900 left Spain with the continental enclave of Rio Muni, a mere 26,000 km2 out of the 300,000 stretching east to the Ubangi River, which the Spaniards had claimed.