As we come to the end of three and half years of often tortuous negotiations over the terms of the UK’s departure from the European Union and the future relationship, hindsight offers some lessons from the ordeal. On some days we saw positive signals from both camps, but on others there appeared to be near-insurmountable obstacles. What is clear now, however, is that the whole process has been a mixed bag, if it’s analyzed using the principles of negotiations we teach in our executive programs…