Britain didn't end the slave trade (technically they only banned the use of British ships). Many British ships sailed under a Portuguese flag, others just took their chances of outrunning Royal Navy ships. Indeed, whole fleets of ships were built that were faster than Navy ships and the government never made any attempt to catch up.

I don't doubt you were taught many things about Britain's serious attempts to end slavery. Some Brits were earnest in their attempts. Others kjust lept on makinmg money.