Previous acoustic analyses of the short monophthongs of younger and older speakers in south-east England demonstrate a convergence in the vowel systems (Torgersen and Kerswill, 2004). Following Wells’s (1982) claim that London is the centre of accent innovation in the south-east, it was suggested that the change was driven by diffusion from London. Analyses of vowels of young and elderly informants in London suggest that, in fact, many young Londoners are engaged in a process of innovation and divergence, not levelling. We find variation between ethnic groups, and this points to inter-ethnic relations as a source of innovation in London English.