A lesson of the past few days is the danger of groupthink. Along with the major international institutions, the assembled might of establishment opinion – in the CBI and TUC, massed legions of economists and a partisan Bank of England – was confident that the existing order here and in Europe would be preserved by promises of unspecified reforms. Until around 2am on the morning of Friday 24 May, the bookies and currency traders followed the playbook that had been given them by the authorities and the pollsters. Then, in a succession of events of a kind that is becoming increasingly common, the script was abruptly torn up. A clear majority of voters had reached to the heart of the situation. Realising that the promises of European reform that had been made were empty, they opted for a sharp shift in direction. The consequences can already be observed: rapid political change in Britain and an accelerating process of unravelling in the European Union. The worldwide impact on markets and geopolitics will be long-lasting and profound.