On September 18th this year, the voters of Scotland will decide in a referendum whether they want their nation henceforth to be independent of the United Kingdom, or remain within the union that has bound Britain together since the Act of Union of 1707.

In "Acts of Union and Disunion", Linda Colley, Professor of History at the University of Princeton, examines the forces that bind together the diverse peoples, customs and loyalties of the United Kingdom. And the often equally powerful movements that from time to time across the centuries threaten to pull Britain apart.

12: Greater Britains

"Between 1815 and 1930, some 19 million people left Great Britain and Ireland permanently in order to live in North America, Australia, New Zealand and South Africa. Initially, many of these outgoing men and women chose to voyage to the lost empire of the United States, but gradually this changed. By the first decade of the 20th century, two thirds of these out-goers opted for Britain's existing settlement empire, the Dominions as they came to be called. If the millions of English, Welsh, Scottish and Irish men and women settling overseas in the empire were to be regarded as "communities of citizens" still owning "the name of Britons" - then what new acts of union would be required in order to sustain their cohesion and allegiance? On what kinds of foundations could Greater Britain, as many commentators chose to call it, durably be constructed?"

Producer: Simon Elmes. Show less