London in the 1930s was something like 98% Anglo Saxon (whatever that is) so I don't buy the idea that the UK was a perennial multicultural society. Most British people at the time had never seen a person from a different race.
The same unease you feel at visiting somewhere like Devon is likely a familiar feeling for white British people when they visit their nation's capital city - they suddenly become the minorities.
It's a difficult subject to beach because it offends just about everyone, but imho it is worth pondering whether a country's capital city should reflect the rest of the populace, or should we live in a world where race is not an issue?
Presumably your family have roots to a non-white country, would it be peculiar for their capital city to become a different majority race?
It seems that it is only Western countries who think this way. There's no way in hell that India, Africa, Russia, the Middle East or China would accept a different ethnic majority in their countries.
It's a bit of a kicker when Jews and Palestinians are always at each others throats whilst still coming from the same area, yet Europeans are expected to happily get along with the rest of the entire world and immediately accept everyone from anywhere as their closest kin.
I understand where you coming from, and I know that growing up in London had given me a very different views to people who have grown up in different parts of the UK. London is not the centre of the universe and being London centric is not good.
As for me, I am white but my family roots are spread and each generation likes moving country like a ping pong ball. My family is very Heinz 57, with members from the UK, Hong Kong, Zimbabwe, Cuba, India, Burma, America, and a hand full of European countries. Christians, Jews, Muslims, Hippies are all represented too, we even have a few Communists.
While the stats for London being 44% white can be shocking to some, you need to put it into context. 63.3% of Londoners are UK born, they are British (English, Scots, Welsh, NI). London is still very much a British city.
Of the 36.7% of Londoners born out side of the UK a percentage of those will be from the EU.
London is/was port city and has always had people from around the world visiting through work (sailors, merchants, etc) so while they might not appear on the census, it does not mean they where not part of London life. If you look at the cartoons of the 18th century of London life, there are many non white faces.
Was London a historic super woke city? No, it was just as racist as the rest of the world at the time, but global trade exposed London to different cultures.