David Olusoga tells the story of attempts to form a united Britain in the 17th and early 18th centuries, a period defined by religious and cultural divisions.

The 20th century sees partition in Ireland. A sense of national unity emerges in the aftermath of the Second World War, but economic challenges in the 1970s create new divisions and questions about the union’s future.

David Olusoga reveals how, in the 18th century, a new British identity was forged in the face of multiple threats from within - including the Jacobite rebellions in Scotland and an Irish revolution in 1798, and near-constant war with France.

The 19th-century union appears secure, but beneath the surface run deep divisions, leading to the emergence of a new working-class movement - and a catastrophic famine in Ireland.