LONDON — Should Britain stumble out of the European Union without a deal and riots erupt in the streets, officials have a plan:

Evacuate Queen Elizabeth II from London, local news outlets reported on Sunday.

Reports of a scenario to save the queen and senior members of her family came to light as the deadline for Britain’s withdrawal from the European Union loomed. With fewer than 55 days until the formal divorce, now set for March 29, the country has been flooded with news of emergency preparations in the event no deal is reached.

Reports of Britons stockpiling groceries, medicines and other supplies have proliferated. Nissan Motor, the automobile giant, confirmed on Sunday that it would manufacture the new version of its X-Trail S.U.V. in Japan instead of Sunderland, in northeast England, where Nissan has been making cars since 1986.

Sony, the Japanese corporation, announced in January that it would move its European headquarters to Amsterdam from Surrey; Airbus and Bentley called the prospect of a no-deal Brexit a “killer” and a “disgrace.”

But the report of an emergency exit plan for the 92-year-old monarch gave a different weight to the possibility of a no-deal Brexit.