The growth of “global cities” in the 1980s was supposed to have involved an occupational polarization, including the increase in low-paid service jobs. Although held to be untrue for European cities at the time, some such growth did emerge in London a decade later than first reported for New York. The question is whether there was simply a delay before London conformed to the global city model or whether another distinct cause was at work in both cases. This article proposes that the critical factor in both cases was actually an upsurge of immigration from poor countries that provided an elastic supply of cheap labor. This hypothesis and its counterpart based on the growth in elite jobs are tested econometrically for the British case with regional data spanning 1975–2008, finding some support for both effects, but with immigration from poor countries as the crucial influence in late 1990s London.