Next week it will be 20 years since Margaret Thatcher fell. Pressure had been building on a number of fronts, but the issue which finally destroyed her was the yet-to-be-born euro. In the last weekend of October 1990, she travelled to a European summit in Rome, where Jacques Delors’ dream of European Monetary Union was high on the agenda. But while Mrs Thatcher was fighting her lone battle against the prospective single currency abroad, she was being fatally undermined at home. Geoffrey Howe, her bitterest cabinet critic, went on television to tell the interviewer Brian Walden that in principle Britain did not oppose the euro.