Honda’s decision to shut its U.K. assembly and engine plant after more than 30 years of production poses the question: are other Japanese automakers manufacturing in the country planning to stage their own Brexit?

Honda, Toyota and Nissan were persuaded to build plants in the U.K. in the 1980s after then-Prime Minister Margaret Thatcher realized that struggling British automakers were not going to be able to sustain a viable automotive industry on their own.

Thatcher pitched the U.K. as the ideal location from which Japanese automakers could sell build cars and export to the European Economic Community, the precursor to today’s EU. Thatcher even told Nissan there was no chance that the U.K. would leave because we would be too dependent on the single market for exports. After the U.K. quits the EU on March 29, that will no longer be true.

“Japanese investors came to the U.K. to access the single market and that was the deal with Thatcher,” Professor David Bailey of Aston University said. “Now that deal has ripped up, they are no longer obliged to stick to that agreement.”

Honda said Tuesday that it will shutter its plant in Swindon near London, along with its plant in Turkey by 2021 as part of a global restructuring. CEO Takahiro Hachigo said the decision was nothing to do with Brexit and was timed to the end of the current Civic's life cycle. However many industry commentators have said that uncertainty around Britain's future trading conditions with the EU will have played a role in Honda's thinking.

Next among the Japanese to make that investment decision is Toyota, which has just started building the new Corolla compact at its plant in Burnaston, central England.

“There are big doubts about that plant if we crash out without a deal,” Bailey said, adding that Toyota could well choose another location when that model comes to an end in 2024.

Toyota has already warned at that a bad Brexit deal puts Burnaston and its U.K. engine plant under threat. “Next time we have to decide investment it would be a big question mark for us,” Toyota executive Didier Leroy said after the vote in 2016. Toyota has an additional reason to ditch its U.K. plant. Starting in 2021 it will take full control of a 300,000-capacity plant in Kolin, Czech Republic, that it set up jointly with the PSA Group to make small cars.

Honda Swindon is the U.K.'s fourth biggest plant ranked on 2018 output at 161,000 units built, with Toyota sixth at 129,000. Both now make just a single model after shifting some production from the U.K. to Japan. Last year Honda moved the CR-V out, citing economies of scale available at its Japanese plants for making electrified versions. This year Toyota will import the Camry hybrid, a midsize sedan that replaces the nonhybrid Avensis that ended production at Burnaston last year.

Nissan, the U.K.’s third Japanese automaker, operates the U.K.’s largest plant by far at Sunderland, which last year built 442,000 cars. Nissan is committed to the U.K. further into the future than either Honda or Toyota with a new Juke small crossover planned for launch this year and a new Qashqai compact crossover, the U.K.’s No. 1 car based on output, expected in 2020.

In January Nissan shocked the U.K. government by making a U-turn on its 2016 decision to move production of its flagship X-Trail utility to Sunderland, despite state financial support. Instead, the model will continue to be built in Japan. The same economies of scale around electrification cited by Honda are likely to be behind the decision, which Nissan blamed partly on the U.K.’s uncertain trading status with the EU.

Exporting from Japan to Europe will become cheaper in time thanks to the recent free trade agreement Japan signed with the EU that gradually lowers tariffs on cars to zero. This is an agreement that the U.K. co-signed as member of the EU and hopes to replicate as it leaves.

The loyalty that the Japanese felt to the U.K. has evaporated and replaced by anger, said Paul Nieuwenhuis, former director of the Centre for Automotive Industry Research at Cardiff University. “The feeling among Japanese business is that they have been let down by the UK government,” he said. “Japanese business is run on trust and the British have proven to be untrustworthy.”