It is four and a half years since Natural England, in response to a ruling from the European Court of Justice, wrote to local authorities covering the catchment of the River Solent regarding nutrient pollution. It was a letter that was to have significant ramifications for housing supply.

Because the level of nutrient pollution in the river was above legal limits, authorities were told not to grant planning permission for new homes unless developers could prove that they would not increase the amount of nitrate pollution entering the river. That is very difficult – and expensive – to do, often needing farmland to be taken out of production, paying water companies to upgrade their sewage works, or creating large-scale wetland habitats on third-party land to filter out pollutants.