One of the perennial questions round these parts is how you decide where a city ends. Should you include the suburbs? Or outlying commuter towns? And so on and so on ad nauseam.
A lot of the time that probably seems like it's mostly of academic interest. In today's England, though, arguments about where to place city limits are having a real political impact. One of the reasons that plans to devolve power to city regions keep grinding to a halt is because of bitter and apparently endless battles about how exactly those regions should be defined.
That’s quite difficult to get your head around, though, so helpfully enough, here are some maps.
Alasdair Rae is a researcher and lecturer in the department of town and regional planning at the University of Sheffield. Using OS Open Map data, he's mapped the built up areas of Greater London, and the four old metropolitan counties that run across the northern belt of England. All five are at the same scale.
You can see a large version here. But even at this size, it’s immediately obvious that some of them have more unity than others.
Greater London (pop: 8.6m) is actually pretty coherent. There are gaps in the city, representing parks in inner London (which is good), and windswept open spaces in the suburbs (which is less good, at least at a time of housing crisis). Nonetheless, the city is very clearly a unit.
Look at Greater Manchester (pop: 2.7m), though, and it’s slightly more obvious that it's made up of individual cities that have merged together. The open spaces are bigger, and the four boroughs that make up the conurbation's northern edge (from west to east, Wigan, Bolton, Bury, and Rochdale) are still almost identifiable by sight.
Merseyside (pop: 1.4m) is clearly split into four zones: Liverpool proper, in the middle; St Helens, lying semi-detached to its east; the Wirral, across the Mersey to the south; and the resort towns of Southport and Formby in the borough of Sefton to the north.
Oddly enough this pattern has almost no connection to the conurbation's government arrangements: the area has five councils, and the bit that looks from above like the city of Liverpool actually also includes chunks of Sefton and Knowsley, too.
Even less coherent is West Yorkshire (pop. 2.2m). You can clearly Bradford and Leeds, the two dense clusters to the north of the region. Outside those, though, the area seems to be made up of smaller cities (Halifax, Huddersfield, Wakefield), towns and even villages. It's not immediately obvious that this is a single metropolitan region at all.
The same is true of South Yorkshire (pop. 1.3m). That's Sheffield in the south western corner; but above it there's an arc of towns (Barnsley, Rotherham Doncaster) with open space between them. See this from space, and you might struggle to identify it as a city.
It's possible to read too much into how buildings are arranged. And there's a danger in confusing cause and effect here, too. Perhaps Greater Leeds has failed to happen because its components are too distinct; perhaps they're too distinct because there's never been a Greater Leeds, which might have filled in the gaps. Perhaps you can’t separate the two.
Nonetheless, maps like these give one possible explanation for why some metropolitan regions have emerged as single cities – and why others simply haven’t.