Last night BBC London News aired a short film I took part in about the Green Belt. As part of a series of ‘authored’ pieces about various solutions to London’s housing crisis, I suggested that we should allow construction on the Green Belt around London to increase the supply of developable land. Land, as Paul Cheshire likes to point out, is the key. The graph above shows how closely house price rises have tracked land price rises. Land-use restrictions on the Green Belt are quite strict: under the National Planning Policy Framework, local councils face a very high burden of proof to approve new developments on Green Belt land. If they were made less strict, then the supply of land and housing would increase and the price of both would fall.

I usually think of people who want to preserve the Green Belt as being motivated by financial considerations. If you own your house, you don’t want its value to fall, so you have a strong incentive to oppose any measure that will increase supply. Perhaps a large proportion of people involved in campaigns to ‘protect the Green Belt’ own their own homes. (And if not, that would certainly falsify this view.)

But filming with the BBC made me realize that this explanation is too neat and too unfair. The preservationist I interviewed, Dr Ann Goddard, was not preoccupied with preserving the value of her home – she believed, as many do, that relatively unspoiled natural areas are valuable and important to protect from development. The meadow she took us to was very pretty and I would regret losing places like it as well. Throughout our conversation Ann made it clear that her idea of England was entwined with its image as a ‘green and pleasant land’, not just somewhere for endless suburban sprawl.

Much of that greenery is worth keeping, but I suggest that the question is not ‘what’ but ‘where’. Since Green Belt land rings cities, it is much more difficult for city slickers to access than, say, gardens or parks. And lots of London already is covered in gardens or parks – more than half, according to one estimate. Allowing London to expand outwards would eat away at the Green Belt, but also allow more people to have gardens and for more (and bigger) parks to be built.

I also realized how important symbols can be: to Ann the meadow we went to WAS the Green Belt. If we’d taken her to a piece of intensive farmland (34% of the Green Belt around London) maybe she would have cared less about the prospect of that being turned into a village. And I wonder if focusing on intensive farmland is the key to changing people’s minds. In the end, if the battle over the Green Belt is about ideas and symbols rather than pocketbooks, a change of language might help us.