This detail from a pen-and-ink drawing shows the captain of a slave ship coming ashore with the trade goods he will use to buy enslaved men, women and children. The ship's crew bring the goods in the longboats, and the local merchant's men help to unload.

The Southwell, owned by Michael Beecher & Co, made two slaving voyages. The first, in 1746, delivered 629 enslaved Africans for sale in Jamaica. the second, in 1748, delivered 284 from Angola to Virginia. This voyage cost £8,000 to fit out - worth just over £1 million in today's values.

Detail from The Southwell Frigate by Nicholas Pocock.