Modern federalism owes much of its distinctive nature to British ideas and practice, from the late 19th and 20th centuries. This book is a review of ideas and practice in the Empire, Britain and Ireland, and Europe. Spinelli's ideas are linked to the British thinkers of the 1920s and 1930s. The book covers such topics as: imperial federation; the idea of a political movement; the relevance of federalism to the Irish problem; and the politics of readjustment and the emergence of federalism.