> London has been multi-ethnic since the 70s or 80s, if not earlier. It is very much a world city.

Leaving aside the Bronze Age structures around the London area and river,

  The archaeologist Leslie Wallace notes, "Because no LPRIA [Late pre-Roman Iron Age] settlements or significant domestic refuse have been found in London, despite extensive archaeological excavation, arguments for a purely Roman foundation of London are now common and uncontroversial."

  Londinium was established as a civilian town by the Romans about four years after the invasion of AD 43. London, like Rome, was founded on the point of the river where it was narrow enough to bridge and the strategic location of the city provided easy access to much of Europe.

above quotes sourced from https://en.wikipedia.org/wiki/History_of_London