It is cheaper for developers to build new homes on greenfield sites because they do not have to pay VAT on them, while they do have to pay VAT on converting and re-using old buildings. This means there is increasing pressure on the countryside as people try to get a slice of the rural idyll. Thursday's Urban White Paper is part of the government's response to the report last year from the Urban Taskforce, which was led by the architect Lord Rogers of Riverside. The BBC's Rory McLean reports.