Complex sentence: Politically, the island is part of the United Kingdom of Great Britain and Northern Ireland, constituting most of its territory: most of England, Scotland, and Wales are on the island, with their respective capital cities-London, Edinburgh, and Cardiff.
Split into simpler sentences: Politically, the island is part of the United Kingdom of Great Britain and Northern Ireland, constituting most of its territory. Most of England, Scotland, and Wales are on the island, with their respective capital cities-London, Edinburgh, and Cardiff.