That might have something to do with London being the biggest financial center in the world after NYC and less with immigration. It's much simpler to reach some easy money when there so much cash slushing around looking for the next hot thing.
Plus the CoL in London also matches the high compensation and sometimes exceeds to the point where despite the high salary it's difficult to feel well paid when you find yourself competing against people with Mc.Mansions.
Plus the CoL in London also matches the high compensation and sometimes exceeds to the point where despite the high salary it's difficult to feel well paid when you find yourself competing against people with Mc.Mansions.