Mr Polanski’s speech was an important one that focused on cost pressures. War in the Gulf means that the affordability question will continue to dominate British politics. The Green party leader showed sharp instincts in advocating policies to bring down rents and energy and household bills, as well as backing wealth taxes. His critique of conservative fiscal rules reflects the broad, well-grounded dissatisfaction with the government’s self-imposed constraints. Mr Polanski’s emphasis on prices, redistribution and fiscal room matters. But he did not deal with productive capacity.