A local dispute about swimmers at Hampstead Heath has now attracted government attention. Environment ministers wrote to the City of London Corporation after video showed crowds swimming in a wildlife pond during last week's heatwave. The swimmers ignored a 'no swimming' sign and disturbed nesting birds. News reports described their behaviour as selfish. But beneath the justified anger lies another question about our access to water. Many feel that natural water no longer belongs to ordinary people. It is being polluted, fenced off or turned into paid attractions.