Boris Johnson has just imposed the most stringent social restrictions on the British public since the end of the World War II.

With immediate effect, the public is being instructed by the prime minister to stay at home. The only exceptions are: shopping for basic necessities; one form of exercise a day; any medical need; and, for the designated key workers, traveling to and from work. If they don't follow the rules, police will have the power to enforce the rules by dispersing gatherings and fines.

The move comes after weeks of criticism that the Johnson has not taken the coronavirus outbreak seriously enough, as Britain's European counterparts had moved faster and harder. In fact, even after this latest announcement, the UK's response is still behind countries like Germany, France and Italy.

What's taken him so long? Johnson is not naturally comfortable with removing anyone's personal liberties. Throughout his career, Johnson has been disparaging about ideas of the "nanny state" and disdainful of the political instincts of those who use the state to tell the public what to do.

In a 2004 newspaper column, Johnson wrote of a proposed smoking ban: "We should have the common sense to listen to others before we presume to act in their interests." Mocking those who were in favor of the ban, he wrote: "Next thing, I said, you'll be wanting to ban drink in order to remove any temptation to get drunk, or ban cars, to avoid ever being tempted to drive too fast…"

Johnson's reluctance to tell others what to do goes beyond gags about drinks. In the same column, he made reference to the Iraq war — and attacked the government of the time (now the opposition Labour party) who "decided, from a position of such ignorance, that the best way to help Iraq was to kill so many of its people."

This stuff runs deep for Johnson. He has spent decades honing his image as a liberal Conservative who believes people should be free to live their lives how they wish. It is a seam which has run through his entire professional career: from editing magazines to running the official Brexit campaign. Johnson has for years defined his political views as driven by personal liberty.

It might go some way to explaining why the new rules might be a little less drastic than they initially sound. Yes, the police can break up gatherings of people and impose fines, but no mention of detention (which would be defensible under human rights law). And the rules will be reviewed in three weeks, the prime minister's advisers were keen to remind journalists.

Yes, these measures are a big deal for the UK, as it slowly comes to terms with how serious this crisis really is. But Johnson will hope that the message towards the end of his address, "no Prime Minister wants to enact measures like this," will have reached the audience at home. And his team will be crossing their fingers that whenever these measures are lifted, it's remembered that this was done with the heaviest of hearts.