“Immigration restrictions are here to stay – but, at the moment, they’re largely based on guesswork.” This was the magisterial conclusion of a recent survey of the subject by my colleague Peter Hoskin. Even the experts don’t know what’s happening.

The point was well made by Iain Duncan Smith, the Work and Pensions Secretary, when he was interviewed on today’s World at One about the new measures announced a few hours earlier by David Cameron, initially to readers of the Daily Telegraph. Mr Duncan Smith pointed out that the last Labour government didn’t even want to know what was going on: it resolutely refused to find out how many foreigners and how many Britons were getting jobs.

For the Government to tighten up what was previously an excessively lax set of immigration rules is a welcome development. Officialdom must at least attempt to get a grip on what is happening. Otherwise public confidence will never recover from its present very low ebb.

But it would be an error to imagine that a perfect immigration system can ever be devised. Nor would a perfect system be desirable: it would mean this country had become a paradise for bureaucrats, and hell for anyone who values freedom.

Many immigrants come here because they value the British tradition of liberty. That is one reason why in many though certainly not all cases they adapt so well to life in this country, and come to think of themselves within a generation or two as British. Which of our leading politicians had a Turkish great-grandfather who knew the Koran by heart? The answer of course is Boris Johnson, and not many people think of him as unBritish. His instinctive understanding of the value of freedom, and refusal to let himself be confined by unnecessary stipulations, help to make him a natural Tory.

Cameron outlined some administrative changes which he claims will address “the magnetic pull of Britain’s benefits system”. These changes are probably worth making, as a sign that we are not, to use another of the Prime Minister’s phrases, “a country that is a soft touch”. But I cannot be alone in doubting whether very many immigrants come here because of the magnetic pull of the benefits system. They are far more likely to come here because they believe they will have the freedom to work hard and make better lives for themselves.

There is sometimes a disconcertingly bureaucratic tone to this Government’s rhetoric. Even in the field of economics, it speaks the language of planning. But the greatest achievements of this country have seldom been planned. They are more often the result of spontaneous development, itself facilitated by an entrenched culture of liberty. Greater freedom under the law, not greater regimentation imposed by the state, for several centuries gave this country a decisive advantage in both politics and economics. Conservatives will never sound entirely convincing when they assert that the solution to questions such as immigration lies in the creation of an efficient bureaucracy.