Almost four years after Johnson promised the fishing merchant the French would be desperate to buy his fish, the business has seen sales plummet 30% and export costs rise by as much as £3,000 a week.

James Withers, chief executive of Scotland Food and Drink, said the situation is a ‘real crisis’ for exporters.

“We were sold a lie by Westminster,” he said in a break in bidding at the market, one of Europe’s largest, but operating at less than one quarter capacity when The National visited.