Britain played a leading part in the Atlantic slave trade, mainly between 1662 and 1807 when British or British-colonial Slave ships transported nearly 3.3 million slaves from Africa. The slaves were taken to work on plantations in British possessions, principally in the Caribbean but also North America. Slavery coupled with the Caribbean sugar industry had a significant role in strengthening and developing the British economy in the 18th century. However, Parliament banned the trade in 1807, banned slavery in the British Empire in 1833, and Britain took a leading role in the movement to abolish slavery worldwide through the blockade of Africa and pressing other nations to end their trade with a series of treaties. The world's oldest international human rights organisation, Anti-Slavery International, was formed in London in 1839.