Boris Johnson’s 570 Billion Reasons for Wanting an EU Trade Deal

Brexit shattered 50 years of trade policy in Britain, divorcing the country from its single largest market. Prime Minister Boris Johnson is now trying to glue the pieces back together.

Since Britain left the European Union on Jan. 31, Johnson has dispatched his foreign secretary on a tour of Australia and Japan to show that Britain is open for business, while his government has pushed the idea of a trade agreement with the U.S.

But there is one market that matters more than any other: the EU. The bloc is by far the U.K.’s biggest trade destination, accounting for 436 ...