That vitiated the government’s goal of curbing social contacts in the face of a new variant of the coronavirus that British officials said spreads far faster than the original strain. Indeed, the escapees from London are likely to spread the virus throughout the country, which reported 35,928 new cases on Sunday.
The prime minister’s foot-dragging on a post-Brexit deal is more tactical. With only 10 days before a Dec. 31 deadline, there would be very little time for a deal to be reviewed in Parliament, where pro-Brexit hard-liners would bring a gimlet eye to it. But with no margin for error, analysts say Mr. Johnson may have to accept compromises to head off an economically ruinous collapse in the talks.
“The contours of a potential deal have been known since at least last March,” said Sam Lowe, a trade expert at the Center for European Reform. “But the P.M.’s modus operandi is to leave tough decisions until the last minute in the hopes that something better comes along — as evidenced by his approach to Covid-19.”
Tim Bale, professor of politics at Queen Mary University of London, said, “The price of this psychological flaw, and of its political consequences, is paid in lives lost, in the case of Covid; whereas with Brexit, it could be livelihoods lost if some businesses go under because of the uncertainty caused by the delay in making a decision.”
With Britain less than two weeks away from quitting the single market and customs union, British companies still have no idea whether their goods will face tariffs if they are exported to continental Europe or Ireland. That could make auto factories unprofitable or drive some farmers out of business.
The trade talks ground on in Brussels on Sunday with no signs of a breakthrough. The two sides are mainly haggling about fishing rights, but there are signs that Mr. Johnson has already bowed to the European Union’s broader demand that Britain accept long-term limitations on its competition policy and state aid to industry.
On the pandemic, critics say Mr. Johnson’s scattershot policies have eroded public trust in the government. He has repeatedly ruled out lockdowns, only to reverse course with the assertion that the scientific evidence had changed. The mixed messages have left many confused and cynical about the rules.
In the latest about-face, Mr. Johnson cited new evidence that the variant was up to 70 percent more transmissible than the original virus — data that he said was presented to his cabinet on Friday. Independent scientists generally back up his concern about the variant. But British public health officials said on Sunday that they had first identified the variant in October from a sample taken in September.
The government first disclosed the variant — as well as concerns that it might spread more quickly — last Monday when it placed London and other parts of southern and eastern Britain into what was then the highest level of restrictions. But two days later, Mr. Johnson reaffirmed his promise to relax restrictions from Dec. 23 to Dec. 27 so that families could get together for Christmas.
When the leader of the opposition Labour Party, Keir Starmer, suggested in Parliament that Mr. Johnson should rethink that plan, the prime minister mocked him. “I wish he’d had the guts to just say what he really wants to do,” Mr. Johnson said, “which is to cancel the plans people have made and cancel Christmas.”
Now, of course, the prime minister has done exactly that — only he waited three more days, during which even more people made travel plans. On Sunday, the Netherlands, Belgium, Italy, France, Germany and Austria all began banning flights from Britain, while the European Union weighed a coordinated response.
Mr. Starmer, predictably, was withering in his criticism, saying that Mr. Johnson was “so scared of being unpopular that he is incapable of taking tough decisions until it is too late.”
The prime minister had given a glimpse into his fears earlier in the week when he alluded to Oliver Cromwell, who discouraged Christmas festivities during the ascetic days of the Puritan movement in England in the mid-17th century. The British papers, which had played up the precedent of Cromwell in the past few weeks, lost no time in tagging Mr. Johnson with it after he announced the Christmas lockdown.
Surprisingly, perhaps, the tough measures by themselves are not unpopular. A poll conducted by the research firm YouGov after Mr. Johnson’s announcement on Saturday found that 67 percent of people said that they supported added restrictions. But 61 percent of people said the government had handled the rollout poorly.
Mr. Johnson, analysts said, was pressured by the same lawmakers in his Conservative Party who are likely to resist a trade agreement with the European Union. To that extent, the pandemic and the Brexit talks have a link.
Because his mismanagement of the lockdown rules has angered some Conservative lawmakers, they said, Mr. Johnson might now calculate that he cannot afford another backlash in Parliament by striking a trade agreement with the European Union that would be unpopular with the hard-line Brexiteers.
Mr. Johnson has navigated such shoals throughout his political career. His deadline mentality — honed during his days as a newspaper reporter and columnist — has sometimes resulted in shrewd decisions.
He dithered for weeks, for example, before backing Britain’s exit from the European Union, even writing essays that argued both sides of the issue. It was a roll of the dice that paid off in giving him a path to Downing Street.
On balance, analysts still predict that Mr. Johnson will come to terms with the European Union in the next few days. But by leaving the final decision so late, the prime minister has raised the odds that, as with the Christmas lockdown, he may have little choice but to accept the offer on the table.
“Johnson’s technique for dealing with problems is to let them run out of control, building to a point of sufficient crisis that delay is no longer viable,” Rafael Behr wrote in a column for The Guardian. “That way, the choice becomes perversely easier because there are fewer options left.”