This article explores an instance of dialect levelling in South East England, the reversal of Cockney diphthong shift. We trace this reversal through an apparent-time analysis of 52 speakers from Debden, a community in Essex with East London heritage. Dynamic vowel analyses of word-list and passage data suggests a reversal of the diphthong shift towards SSBE targets which has occurred most abruptly in those born after 1992 potentially as a result of increased social mobility in this generation. We compare the results in Debden to previous findings in the south-eastern towns of Milton Keynes and Reading where apparent-time change was also observed away from a shifted vowel system and towards SSBE targets (Kerswill & Williams 2000, 2005). In diverse areas of South East England, a common process of levelling towards the pan-regional standard is present which is not occurring exclusively as a result of dialect contact or face-to-face interaction. Nonetheless, each community exhibits a distinct trajectory and timing of language change which can be attributed to different patterns of movement and resettlement and, in particular, access to social mobility and the retention of community networks.