LONDON—British Prime Minister Boris Johnson has finished a rocky year on a significant be aware, with a absolutely free-trade agreement with the European Union less than his belt and mass vaccination versus Covid-19 less than way.

Now that the place is unconstrained by most EU rules, he has a when-in-a-generation political prospect to reshape the U.K. and define its put up-EU direction. The large unidentified is what he will do with that prospect.

Brexit was billed by some of its longtime advocates as a way of unleashing a new dynamism in Britain by ditching Brussels’ purple tape to make a small-tax, freewheeling “Singapore-on-Thames”—a phrase coined by a prior British Treasury main, Philip Hammond—selling its products and companies across the world.

But Mr. Johnson is not a absolutely free-current market Conservative in the mildew of Margaret Thatcher. He has so considerably promised Britons far more regulation, not much less, with bold programs to increase the minimal wage and control greenhouse-gasoline emissions. He has promised far more condition paying, not much less, in get to “level up” an financial system he suggests is way too dependent on London and southern England.

These policies enabled him to earn large in past year’s election in districts ordinarily hostile to the ruling Conservatives, when his dogged pursuit of Brexit alienated numerous of his party’s standard allies in corporate boardrooms. All these tensions current a puzzle: If Mr. Johnson does not want an additional Thatcher-model financial revolution, what does he want to do with Britain’s freedom from Brussels?