In theory, Imperialism, the principle, spirit, or system of empire, is driven by ideology, whereas Colonialism, the principle, spirit, or system of establishing colonies, is driven by commerce. In practice, it is often difficult to distinguish where one ends and the other begins.

Historians make a distinction between two British empires, dating the first from the seventeenth century, when the European demand for sugar and tobacco led to the development of plantations on the islands of the Caribbean and in southeast North America. These colonies, and those settled by religious dissenters in northeast North America, attracted increasing numbers of British and European colonists. The late seventeenth and early eighteenth centuries saw the first British Empire expanding into areas formerly controlled by the Dutch and Spanish Empires (then in decline) and coming into conflict with French colonial aspirations in Africa, Canada, and India. With the Treaty of Paris in 1763, the British effectively took control of Canada and India, but the American Revolution brought their first empire to an end.

Captain James Cook's voyages to Australia and New Zealand in the 1770s initiated a further phase of territorial expansion that led to the second British Empire. This reached its widest point during the reign of Queen Victoria (1837–1901). At no time in the first half of her reign was empire a central preoccupation of her or her governments, but this was to change in the wake of the Franco-Prussian War (1870–71), which altered the balance of power in Europe. During the next decades, two great statesmen brought the issue of imperialism to the top of the nation's political agenda: the flamboyant Benjamin Disraeli (1804–1881), who had a romantic vision of empire that the sterner William Ewart Gladstone (1809–1898) distrusted and rejected. Disraeli's expansionist vision prevailed and was transmitted by newspapers and novels to a reading public dramatically expanded by the Education Act of 1870. >> note 1

Symbolically, the British Empire reached its highest point on June 22, 1897, the occasion of Queen Victoria's Diamond Jubilee, which the British celebrated as a festival of empire. It was "a Roman moment." The analogy of the Roman Empire was endlessly invoked in discussions of the British Empire. It figures, for example, at the start of Conrad's novel Heart of Darkness >> note 2 and in "Embarkation," the first of Thomas Hardy's "War Poems."

The Roman Empire, at its height, comprised perhaps 120 million people in an area of 2.5 million square miles. The British Empire, in 1897, comprised some 372 million people in 11 million square miles. An interesting aspect of the analogy is that the Roman Empire was long held - by the descendants of the defeated and oppressed peoples of the British Isles - to be generally a good thing. Children in the United Kingdom are still taught that the Roman legions brought laws and roads, civilization rather than oppression, and in the second half of the nineteenth century, that was the precedent invoked to sanction the Pax Britannica. >> note 3

In 1897 the Empire seemed invincible, but only two years later British confidence was shaken by the news of defeats at Magersfontein and Spion Kop in the Anglo-Boer War. Those and other battles were lost, but eventually the war was won, and it took two world wars to bring the British Empire to its end. Those wars also were won, with the loyal help of troops from the overseas empire (more than 200,000 of whom were killed in World War I alone). In return, however, the countries of the overseas empire wanted a greater measure of self-government, and, in 1931, the British Parliament recognized the independent and equal status under the Crown of its former dominions within a British Commonwealth of Nations. Following World War II, most of the remaining imperial possessions were granted independence; and fifty years after Queen Victoria's Diamond Jubilee, India, "the Jewel in the Crown" (Disraeli's phrase), was cut in two to become the Commonwealth countries of India and Pakistan. The most recent development in the dismantling of the British Empire was the restoration to Chinese rule, under a declaration signed in 1984, of the former British crown colony of Hong Kong, on the southeastern coast of China. The Union Jack was finally and symbolically lowered on July 1, 1997, in a ceremony attended by the last British governor of Hong Kong, Chris Patten.

So, one by one, the subject peoples of the British Empire have entered a postcolonial era, in which they must reassess their national identity, their history and literature, and their relationship with the land and language of their former masters.