Every new government – at least for the past decade or so – has come into office with a promise to build more homes. New ministers don a hard hat, take a trip out to a recently completed development and smile indulgently as a bright young couple get given the keys to a smart-looking new-build. Then follows a speech about aspiration. The unspoken truth will be that it is not up to the minister how many new homes are built in his or her term.