"I think the first what would happen in the immediate wake of a hard Brexit is a lack of confidence in UK economy. Business is already telling me that they need a year or so to adjust to what is going to change in March 2019. Without a deal, tariffs would immediately kick in and we would need all the physical attributes of a customs border. And that is just the trade aspect. Imagine what would happen if, from one day to the next, we had no aviation agreement or no agreements for dealing with security across Europe."