For 176 years, Britain was the governing European power of what would become their American colonies (1607-1783). Thomas Jefferson was only one American under total British rule who legally petitioned for an end to slavery in the colonies, only to be rejected by that same British rule. What Jefferson really felt about Britain's repugnant role in American slavery can be found in the passage he wrote charging the King with that repugnance in The unanimous Declaration of the thirteen united States of America. Unfortunately, Jefferson's passage on slavery was edited out of the published Declaration by the Continental Congress.
The American colonies won their independence from British rule and existed as 13 sovereign States from 1783-1789. The United States of America was ratified in 1789.
So, after centuries upon centuries upon centuries of slavery forcefully instituted in America, it took just 82 years for the United States to completely abolish horrendous human slavery and inhumane involuntary servitude forever under its jurisdiction, with the 13th Amendment to its Constitution ratifying it and approximately 1 million lives - of all races - sacrificed during its "civil war", thus paying in blood for that freedom for all.