More than half of large companies have already put emergency contingency plans into action, according to a new survey, and in key sectors such as insurance and transport there are warnings of higher prices and disruption for customers if the fragile truce breaks down.

British and EU governments last week agreed to postpone discussions over Northern Ireland in order to provisionally agree that a 21-month transition phase could begin after March 2019, but only so long as outstanding disagreements are solved nearer the time.

The fudge has met with scepticism in the City, where leading law firms such as Ashurst and DLA Piper warn it “provides no legal certainty.” A survey by the law firm Pinsent Masons found 51 percent of companies had now triggered their plans for a no-deal Brexit, including shifting work abroad to European subsidiaries.

Some lobbyists are instead calling on the Bank of England and other regulators to allow them to act as if the deal were watertight in order to avoid further disruption. “Without such political guidance, firms will have to assume that March 2019 is the U.K. exit date and plans will need to be executed accordingly,” warned Stephen Jones, chief executive of U.K. Finance, which represents banks and mortgage lenders.

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