Prime Minister Theresa May has said she wants a customs arrangement with the European Union which allows trade to be "as frictionless as possible," but few expect goods will be able to continue to move as seamlessly as they do within the bloc.
"The nightmare scenario is actually having physical customs borders ... it would be absolutely a catastrophe for the ports and for our sector," Guy Platten, Chief Executive of the UK Chamber of Shipping, told reporters. "You've suddenly got lorries stacked up, you've got sailings canceled ... the whole supply chain is completely affected."
The chamber says 95 percent of Britain's international trade is moved via ship, and the industry supports 250,000 jobs.
Dover on the southeast coast of England, Europe's busiest ferry port, currently handles around 500 non-EU trucks a day and around 8,000 from the EU, he said.
If the EU trucks faced the same customs checks as the non-EU trucks the whole process will be slowed, particularly impacting goods such as fresh food, he added.
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