Abstract Linguistic research refers to many related accents in Southeast England: Standard Southern British English (SSBE), Received Pronunciation (RP), Estuary English (EE), Cockney and Multicultural London English (MLE). However, there is inconsistency and imprecision in the demarcation of these accents based on linguistic and social factors. This paper delineates accents in Southeast England based on patterns of linguistic co-variation which we then relate to social predictors. We applied functional Principal Component Analysis to F1 and F2 measurements for diphthongs extracted from wordlist and passage productions for 193 young, south-eastern speakers. Principal Components were entered into a clustering analysis that identified patterns of linguistic co-occurrence. Three clusters emerge, broadly aligning with SSBE, MLE and EE for both linguistic and social factors. We illustrate the linguistic centre of gravity of the three diphthong systems for use as reference points in future research, and we discuss the need to make explicit how accents are defined.