The Long and Difficult Road to a U.S.-U.K. Trade Deal

Politicians on both sides want it, but it’s a political challenge for British officials

The British government has said it wants to leave the European Union’s customs union so it can pursue trade deals elsewhere in the world. Of those, the biggest prize would be an agreement with the U.S., the U.K.’s biggest national trading partner.

Politicians on both sides of the Atlantic, including President Donald Trump, have spoken enthusiastically about a U.S.-U.K. free-trade deal.

But...