British commercial interest in the American colonies o f Spain and Portugal has a long history, but the relationship was completely transformed in the first quarter o f the nineteenth century. Three sets o f events provide the context for this change: the growth o f industrial production and exports in Britain; prolonged war in Europe, in which Spain was initially allied with Britain but then, from 1796 until 1808, with France; and the process o f emancipation in Latin America, which began with the de facto independence of Buenos Aires in 1810 and lasted until 1825. The speed with which the situation developed was unexpected, especially after the British victory at Trafalgar in 1805 which destroyed French and Spanish naval power. This was quickly followed by Napoleon’s institution o f the ‘Continental System’, which effectively barred British exports from European markets and forced merchants and manufacturers to search for other outlets. Also in 1806 a Royal Navy officer, Com modore Home Popham, launched an unauthorised attack on Buenos Aires. While this episode ended in defeat for the British, it provided a catalyst for the growth o f discontent with Spanish rule in the River Plate. Then, in 1807-08, Napoleon invaded the Iberian peninsula, bringing into question the whole issue o f Spain’s relations with its colonies, and further stimulating the incipient movements for independence.