The English planning system has always frowned on places merging together. Whether it’s “strategic gaps”, “green corridors” or the Green Belt purpose “to prevent neighbouring towns merging into one another”, coalescence is assumed to be a dirty word. It’s time to challenge this – the economics is clear, we need bigger cities, not more towns.
Identity
The assumption is so deeply embedded in policy as an article of faith that it is rarely spelt out why our urban areas must be kept fragmented in separate towns. At most we may get a passing reference to local identity. But we don’t stop to ask if this is really true, nor to count the costs of strangling the natural growth of cities.
Identity is a subtle thing. I suspect most residents of Wolverhampton or Oldham, for example, retain that local identity despite continuous urban fabric joining them to Birmingham and Manchester respectively. And a 20 metre gully of Green Belt passing under the A647 is not why the people of Bradford remember they’re not in Leeds. Identities can and do survive coalescence into conurbations – just ask Croydon or Epsom.
Agglomeration
It is a well-established consensus in economics that people benefit from being together – bigger and better-connected places tend to be richer than more isolated communities. In many ways the story of economic development is one of urbanisation. And when cities are allowed to grow they naturally swallow neighbours to become conurbations, but we seem to have forgotten that this is a good thing, and it happens because people want to live there.
The world’s great cities are a roll call of successful coalescence. When the cities of London and Westminster merged, the result was pretty effective! Likewise Brooklyn and New York, Buda and Pest. And would Silicon Valley be the powerhouse it is now if planners had preserved the isolation of San Francisco, Palo Alto and San Jose?
Yet in England we try hard to ensure no great city can ever emerge again. The result is that our second-tier cities are often poorer and less productive than their peers in comparable countries. In large part, as Tom Forth has rightly pointed out, this is because we don’t invest in efficient transport – without trams or a metro system a city has a smaller effective size or catchment. But more broadly, it is the result of the planning system’s aversion to coalescence. Through greenbelt and other policies, we have frozen places such as West Yorkshire or Greater Manchester into perpetually half-formed cities, a collection of smaller places caught in the act of conurbation, but never allowed to consummate.
Building for sustainability
Other things being equal (where landscape or ecology allow), rather than preserve the separation of towns, we should actively embrace their merger. We need to build a lot more housing, and the most sustainable place to build is likely to be in that gap that joins two places into a greater whole.
That is a place people want to live, it gives access to both places, twice as many jobs, twice the range of retail and leisure, twice the choice of public services. Filling in that gap benefits the economy too – business in both places get access to a larger customer base, and a larger labour market. And it makes public services cheaper to provide, and easier to hit the critical mass needed to sustain everything from hospitals to bus services.
These gaps will already have access to a much better range of existing infrastructure, including transport links, than more isolated places on the other side of a town. And concentrating development in the corridor between towns strengthens the case for investment in rail, tram or bus connections in a way scattered growth elsewhere never will.
The English planning system was born from a reaction to the pollution and disease of 19th century cities. The response was often to “start again” with planned new towns, while stopping cities from growing. In the 21st century it’s time to recognise this is making us poorer. Our cities are too small. It’s time to plan for the healthy and liveable conurbations of the future. Bring back coalescence.
Barney's Blog 
I don’t think many people would disagree with you about expanding London, or I think it’s more of a boundary correction. We have had so many conversations/meetings on this subject the outer boroughs are all ready primed…So who is dragging their feet?
Of course they don’t, but currently we have a huge shortage of housing in cities because a lot of people do want to live where the jobs and services are, but we’ve frozen city boundaries to make it hard for people to live where they would like to. There’s a really interesting moral/political debate to be had about how we weigh up the wishes of people who already live in a place, vs the wishes of those who would want to live there if we let them.
Maybe not everyone wants to live in a city or town? Maybe because the benefits for current residents are likely to be intangible and many years away at best, and the downsides are immediate and very apparent? If agglomeration is so important to you, make a better case to pay the premium required to densify existing cities and towns.