The black man in that video is spreading the LIE the English love to tell themselves, that it was THEY who ended slavery.
Parliament passed the Slavery Abolition Act in 1833 but that only ended slavery in the British isles and her Caribbean holdings, not in her African and Asian holdings.
Slavery continued apace in British East Africa (modern-day Kenya) until the 20th Century. And “Mui Tsai,” a form of (non-chattel) slavery peculiar to Asia, flourished in British Singapore and Hong Kong. The Brits returned control of Hong Kong to China in 1997 and Mui Tsai was known to still be occurring there as late as 2005. And Hong Kong is today considered the gateway to human trafficking in Asia.
So the formerly great British might be fond of dislocating their shoulders, patting themselves on the back over (allegedly) stamping it out, but slavery was long gone in the USA before it ended in the British Empire.