Complex sentence: Pornography in the United Kingdom has existed since Great Britain was formed by the Acts of Union 1707, the United Kingdom was subsequently formed by the Acts of Union 1800, and before that in the four countries of which the kingdom consists.
Split into simpler sentences: Pornography in the United Kingdom has existed since the United Kingdom was formed by the Acts of Union 1800. Before that it was found in Great Britain which was formed by the Acts of Union 1707, and earlier still in the four countries of which the modern kingdom consists.