One of the most common features of vernacular dialects of English around the world is the use of non-standard 'was' or 'were' in place of standard alternatives, e.g. "it were nice"; "my sisters was here". In some dialects, this variation is levelled towards 'was' or, less commonly, 'were'. The linguistic constraints that apply to any 'was/were' system also vary regionally, because of competition be-tween supralocal tendencies and more localized patterns of use. This study presents a comparative sociolinguistic analysis of these factors in over 4,700 tokens of 'was/were' from four cities that represent distinctive dialect areas of England: Newcastle upon Tyne (North East), Leeds (West Yorkshire), Nottingham (East Midlands) and Southampton (South). The results show that while Newcastle, Nottingham and Southampton have 'was'-levelling, Leeds has 'were'-levelling. However, the 'were'-levelling system in Leeds is depleting over time, with non-standard 'were' decreasing in frequency and the younger generation adopting the supralocal trend of using singular agreement with existential 'there', which is already robust in the other three cities studied. We also observe that non-adjacency of subject and verbs correlates with non-agreement more generally. The research contributes to our understanding of agreement in contemporary dialects of English and establishes the relative pull of particular linguistic forces in the context of ongoing dialect levelling.