Do the costs of food store development in town centres outweigh the benefits? It’s time we moved on from the dogmatic, polarised positions that have underpinned this debate over the past 20 years. The only way to do that is to gather hard evidence at local level, to which the Portas review regrettably contributed nothing.

Fortunately ongoing work by a team at Southampton University is throwing valuable light on local dynamics. Researchers investigated the impact of large corporate food stores on central and edge-of-centre sites in four market towns and four district centres between 2007 and 2009. They then looked at the impact of small store development in five small towns in 2010/11.

They found these developments had had a positive impact on those centres, for example by retaining retail spending that might otherwise have been lost, spreading this retained spending to existing retailers and services through linked shopping trips, and anchoring the existing retail structure through the downturn.

They also found the new stores were strongly welcomed by local shoppers and not widely seen as a threat by existing traders. Nor had the retail diversity of these centres suffered.

“The stores were strongly welcomed and not widely seen as a threat”

Lest these results should be dismissed as aberrant, researchers at Stirling University have investigated the impact of a Tesco superstore in Shettleston, a deprived area of Glasgow showing signs of retail deterioration prior to Tesco’s arrival in 2003. Far from devastating the local structure, this development has stabilised it and reinforced localness.

Other local studies may well come up with different conclusions. If and when they do, they will add to our understanding of local dynamics and tell us more about why some town centres are more resilient than others. Impact assessments, with their limitations, have their part to play, but there is no substitute for rigorous, ex post facto analysis.

Did the supermarket salesmen deliver on their promises? Or were the local traders decimated? Above all, what are the implications for policy? As the American wit Josh Billings observed: “The trouble with people is not that they don’t know, but that they know so much that ain’t so.”