Alnwick, Northumberland, is a market town with beaches, a handsome castle and one of Britain's best second-hand bookshops, Barter Books. A coffee was being sold for £3.60, which even some cafés in Notting Hill would blush before charging. The flat white is what a litre of unleaded or an 800g sliced white loaf is for others: an anchor price that immediately allows one to judge the state of the consumer economy.