The precise location of the north-south of England divide is a fraught question that has been debated for centuries, drawing on factors ranging from economic prosperity and political views to the pronunciation of the word “scone”. Now, scientists have entered the fray, proposing an objective, machine learning-based analysis of the distribution of Pret a Manger and Greggs shops across England.
The AI-based approach places the critical dividing line at which avocado wraps give way to sausage rolls close to the M1 Watford Gap services and concludes that Birmingham, Coventry and Leicester, which often fall into a disputed grey area, should be considered “northern”.
“The food we eat is a very good indicator of whether someone is northern or southern. Greggs is very popular in the north, where people do seem to prefer a steak bake,” said Dr Robin Smith, the physicist at Sheffield Hallam University who led the study, adapting an algorithm normally used to study nuclear reactions.
“We are fascinated by the north-south divide, so it is good to have a way of working out where it starts.”
A secondary analysis, based on the distribution of Waitrose and Morrisons supermarkets also places the divide within a few miles of the Watford Gap (distinct from Watford, in Hertfordshire).
“The north really may start at the Watford Gap, just as people say it does, even though, as someone from Birmingham, I wouldn’t think of myself as being from the north of England.”
Some historians have dated the north-south divide to 1069, when William the Conqueror charged north “like a raging lion” to try to control the more unruly population. Greggs has its roots in the north, opening its first shop in Tyneside in 1951, while Pret, which first opened in Hampstead in north London in 1984, has its shops concentrated in the south-east. However, a shift may be under way, Smith said.
“Since Greggs produced the vegan sausage roll … it has become more popular in the south, so this might not be a marker of northernness for that much longer.”
The analysis, published as a preprint in April, was highlighted this week at the Cheltenham Science festival.
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“There’s a lot of debate, but thankfully mathematicians have worked this out,” Sophie Maclean, who is due to begin a PhD in number theory at King’s College London, told the audience. “Really there is only one way to judge what’s north and what’s south and that is by looking at the distribution of Pret and Greggs.
“You could imagine the single Pret in Newcastle surrounded by a swarm of Greggs,” Maclean added. “In London, they say you’re never more than 6 metres from a rat – or a Pret.”
Researchers used an artificial neural network model to identify the “optimal” north-south line dividing the most Greggs from Prets. The analysis was adjusted to take into account the larger number of Greggs in total. This produced a diagonal line running from just above Poole, via Watford Gap, to just below Skegness and then dipping down to take in the north coast of Norfolk, with King’s Lynn falling north of the divide and Norwich lying to the south.
Despite being geographically the southern-most point of England, the algorithm, categorised Cornwall as “northern” based on consumption habits, but this was put down as an anomaly due to the lack of data: there are only two Greggs and no Prets in the county.
The line follows a remarkably similar path to divides based on gross household income, with incomes in the north generally being lower than in the south, and the “Dorling line”, based on factors including house prices, employment level and life expectancy.