I’m no Briton and i just know a few bits here and there of British history, but isn’t the UK a traditionally mostly white country ?
I’m guessing half of say, Norwegians, also can’t name a black Norwegian historical figure either. I’m betting it’s even more than that and they’re the most immediate neighbors of the UK.
I’m not saying they’re not important to be remembered, or that there weren’t black people in Europe since the Roman times, here and there, but statistically speaking, black people were the overwhelming minority.