In this paper we explore for the first time regional differences in the patterning of occupational social mobility in the UK. Drawing on data from Understanding Society (US), supported by the Labour Force Survey (LFS), we examine how rates of absolute and relative intergenerational occupational mobility vary across 19 regions of England, Scotland and Wales. Our findings somewhat problematise the dominant policy narrative on regional social mobility, which presents London as the national 'engine-room' of social mobility. In contrast, we find that those currently living in Inner London have experienced the lowest regional rate of absolute upward mobility, the highest regional rate of downward mobility, and a comparatively low rate of relative upward mobility into professional and managerial occupations. This stands in stark contrast to Merseyside and particularly Tyne and Wear where rates of both absolute and relative upward mobility are high, and downward mobility is low. We then examine this Inner London effect further, finding that it is driven in part by two dimensions of migration. First, among international migrants, we find strikingly low rates of upward mobility and high rates of downward mobility. Second, among domestic migrants, we find a striking overrepresentation of those from professional and managerial backgrounds. These privileged domestic migrants, our results indicate, are less likely to experience downward mobility than those from similar backgrounds elsewhere in the country. This may be partly explained by higher educational qualifications, but may also be indicative of a glass floor or opportunity hoarding.