One of the key mistakes was to enter the ERM at a time when German interest rates were soaring due to the strains of reunification. That, at least, should not be repeated. But another crucial error was was to join at too high a rate - with sterling at 2.95 marks. Today, as the debate on euro entry steps up, sterling is at the equivalent of 3.11 marks. The danger of getting it wrong a second time is all too clear.