Sugar and slaves
Silk, cotton, and tobacco were important for the growth of English trade, but not as important as sugar. Between 1600 and 1750 people began to eat much more sugar with their food. The sugar came from the West Indies, where the cane grew in 'plantations'.
Ships laden with sugar (and rum) sailed from Barbados to Bristol and Liverpool. Factories there refined it (made it pure). Then it was sold to merchants in English towns and cities, or abroad.
The owners of the plantations were rich English landlords. Many of them stayed at home, and lived on their profits. They had agents in the islands to manage their estates. The hard work of cutting and carting the cane and milling the sugar was done by black slaves.
The slaves came from West Africa. A lot of them were prisoners, captured in wars between tribes. Their captors sold them to white slave-traders, or exchanged them for cloth, metal goods, or guns from Europe. The traders branded them with their marks, and packed them into ships. The voyage to the West Indies took about eight weeks. A quarter of the slaves died at sea.
The slaves were sold in the West Indies to the planters' agents. There was always a brisk trade, for slaves lasted only a few years in the cane fields. Meanwhile, the ships were loaded with sugar and rum, and set sail for home. The trade made the merchants and planters rich. Most of them never saw the inside of a slave ship.
Walter Robson: Crown, Parliament and People; Oxford University Press, 1992/2002, page 72