This may be a point on English and if it’s not your first language apologies. But once people are in London they are immigrants, they are emigrants from their country of origin.
Then for London. 63% of the population are British born, so it’s not over 50% at all. If you include the proper Metro area of London then that drops further to be even more British. The only thing London is is that it isn’t 50% white British but that’s not to do with immigration. As for poorer countries, no? 12% are from EU countries which aren’t really poor. Then loads more come from the US, Canada, New Zealand, Australia etc, also not poor. Then the massive majority of “poor”, if you want to describe it that way, countries are Commonwealth countries so there’s a pre-existing relationship there and most of them moved to London in the 50s through 70s. So it’s not even new or worth mentioning.
EDIT: Also for the feels. Londoners don’t really seem to give much of a shit really.
EDIT2: London is the capital city of Britain so yknow not just the English.