Britain's Hidden Slave Trade Historian John Gilmore and writer Angelina Osborne visit four places connected with the British slave trade to tell their stories and reflect on their legacy. 4/4. Westminster Hall was the venue for one of the slave trade's most significant heavyweight contests in the 18th century, which resulted in slavery being effectively banned in England. In the red corner, one of the unsung heroes of abolition, Granville Sharp, and in the blue corner for the establishment and the status quo, Lord Chief Justice Mansfield.