Alexander Falconbridge, like his wife, was a native of Bristol. Wishing to adopt a medical career, he spent a year as a student at the Bristol Infirmary. Then, having no financial means to set up a practice of his own, he signed on as a surgeon on a slave ship, a potentially lucrative position, since surgeons received, as well as their pay, a bounty of a shilling a head for each slave landed, and, if they survived a few voyages, might then be taken on as a captain.

Between 1780 and 1787 he made four voyages. ‘In my first and second voyage’, he later declared, ‘I reflected but little on the justice or injustice of the Trade; in my last voyage I reflected more, and the more I did so the more I was convinced it is an unnatural, iniquitous and villainous trade, and could not reconcile it to my conscience’. He therefore gave it up, and when Clarkson met him, was living at home, in debt to his father, hoping to improve his chances by studying with a well known Bristol doctor.

Clarkson passed on Falconbridge's devastating evidence to the newly constituted Committee for the Abolition of the Slave Trade. It was decided to publish it, and circulate it widely as propaganda. Falconbridge came to London, supporting himself by working in a dissecting establishment, and was helped by Richard Phillips, a Quaker lawyer, to put his evidence into publishable form. Phillips's daughter recalled long after —

Falconbridge also gave evidence to a Committee of the Privy Council set up to investigate the trade in slaves.