The moment of truth is arriving for the more than 1,000 Japanese firms that are based in Great Britain as the prospect of the dispute over Brexit looks set to continue well into the next decade.

In the 1980s, British Prime Minister Margaret Thatcher persuaded Japanese industries and finance houses to use London and the regions of England as their base to sell into the rest of the European Union. She was the architect of the Europe Single Market and led the charge to abolish all national protectionist rules to allow foreign firms in Britain to sell into Europe.

Now there is $77 billion worth of Japanese invested in the United Kingdom. More than 1,000 firms employ 140,000 workers. The big Japanese auto firms produce 800,000 cars, mainly for export to the EU market. Most of the components in Japanese automobiles made in England are produced in continental Europe and taken by trucks on a just-in-time basis to Nissan, Honda and Toyota plants in England.