The abandonment of James Island and the founding of Bathurst (1815), now the capital city, Banjul, was born out of Britain’s war against slave trading in the 19th century.As the River Gambia was recognized as a British possession by Treaty of Versailes,1783, the passing of the Abolition Act of 1807 made slave traffic on the River unlawful. However, the French, Portuguese, Spanish and Americans continued to trade in slaves. Situated on the mouth of the River, Banjul was more strategically placed than James Island for controlling the entry and exit of river traffic. In November 1815, Sir Charles MacCarthy ordered Captain Alexander Grant to proceed from Goree (a fortified Island to the north, off the coast of Senegal, now a World Heritage Site) with a detachment of the African corps to examine the viability of establishing a military strongpoint on Banjul Island.

Soon after acquiring the Island from the King of Kombo, Grant started work on a barracks to house 80 men and on the erection of a battery of six 24 pounder guns and two field pieces (This battery forms part of the World Heritage Complex under James Island and Related Sites)The idea was that the battery could afford sufficient fire power to stop any ships trying to run out of the river mouth and that their capture could then be effected by naval vessels on patrol. Within months of setting up the base in Banjul, five slave ships were captured.

However, it soon became apparent that the Battery’s fire power could not traverse the entire width of the river mouth which is about 8 miles at this point. Ships could easily escape by moving closer to the north bank of the river. Fort Bullen was therefore constructed around 1827 on the north bank.