because black or people from outside the UK or even Europe would be very very uncommon in the 12th or 13th century.
You can walk from the uk to Africa (with a boat trip or 2) in a couple of months
Trade routes from Europe to Africa were established by the bronze age, romans & then vikings had extensive trade with North africa, slaves as well as goods, tho you shouldn’t assume black person = slave.
By the middle ages pilgrimages, war & trade with middle East and beyond was not uncommon
Anyway back to dreadful remaking…
https://movieweb.com/liam-neeson-naked-gun-reboot-update/