The Competition Commission's analysis in 2007 of entry and exit conditions among small stores across more than one thousand British high streets provided a landmark piece of research on a topic in which debate and policy recommendations had moved significantly, and arguably dangerously, ahead of the available evidence base. Within a general context of a continuing long-term decline of specialist small stores in British town centres and high streets, it cast considerable doubt on the popularly held view that a broad-based decline of the independent convenience store sector was taking place across the UK, or that Britain's high streets were experiencing an accelerating decline in their small and specialist stores. Additionally, and even more controversially, the Commission's analysis was able to demonstrate that competitive entry by larger format corporate food retailing was not inevitably and uniformly associated with negative impacts on the small store sector. It is known that the Commission's research was paralleled by an identical analysis conducted on behalf of one of the main parties to the Groceries Market Inquiry by the University of Southampton. The first component of the Southampton analysis, which both corroborated and extended the Commission's findings, is available in the public domain. This paper now presents the second component of the Southampton analysis, which similarly both corroborates but also extends the vitally important ‘conditional entry’ dimension of the Commission's research—focusing directly on the extent to which entry into the small store sector during the early to mid 2000s might have been constrained by, and exit from the sector accelerated by, the competitive impacts of larger format foodstore openings by the major corporate retailers. The paper shows: (a) that there is an important missing regional dimension within the Commission's analysis, and (b) that entry and exit into the small store sector in the UK during 2000–06 was constrained and/or accelerated by the competitive impacts of supermarket opening in a different fashion within ‘London and prospering southern England’ than elsewhere in the country. That is to say, in the region of the UK in which arguments about the threat of corporate retail to the diversity of the small store sector had often proved particularly heated, the Southampton analysis shows small shops in town centres and high streets to have been more robust to the competitive opening of larger format corporate foodstores than elsewhere in the UK. In that context, the paper suggests that the findings represent an ‘inconvenient truth’ which deserves consideration both in policy debate and in future processes of planning regulation reform. Discussion of the relevance of the findings in respect of the proposed changes to Planning Policy Statement 6 released for consultation by the Department for Communities and Local Government in July 2008 is presented.