One of the most controversial aspects of the British Empire is its role in first promoting and then ending slavery. In the 18th-century British merchant ships were the largest element in the "Middle Passage" which transported millions of slaves to the Western Hemisphere. Most of those who survived the journey wound up in the Caribbean, where the Empire had highly profitable sugar colonies, and the living conditions were bad (the plantation owners lived in Britain). Parliament ended the international transportation of slaves in 1807 and used the Royal Navy to enforce that ban. In 1833 it bought out the plantation owners and banned slavery. Historians before the 1940s argued that moralistic reformers such as William Wilberforce were primarily responsible.