After a February meeting between U.K. Prime Minister Theresa May and 19 Japanese business chiefs, Tokyo's ambassador to Britain warned what might happen if Brexit took an unfavorable turn for foreign investors.

"No private company can continue operations" in the U.K. if it becomes unprofitable, Koji Tsuruoka told reporters on the steps of May's Downing Street residence, after the premier pledged to pursue frictionless trade with the European Union. "It is as simple as that."

Eight months later, as the risk of a no-deal Brexit looms larger and nearer, Japanese companies aren't waiting around to find out whether May can deliver. Instead, a growing number of them are heeding Tsuruoka's warning, shifting operations out of the U.K. or threatening to scale back if the country crashes out of the EU without a deal.