Just before the hacking scandal broke, the Sun sent a young and by all accounts decent reporter to meet a woman who said she had a story — a ‘walk-in’ as we call them in the trade.

The walk-in produced a phone and said the Sun would want to take a look. One picture on it showed the face of a much-loved TV presenter. The rest of the celeb’s body was more lustful than lovable, however, as he was exposing his member in triumphant fashion. Accompanying the picture was a lot of explicit sex talk. The phone looked as if it belonged to the star’s mistress, and the very famous and very married presenter had been sending her pornographic ‘selfies’ and sex texts to remind her of the joys that awaited her when they next met.

The reporter took the phone. Contrary to received wisdom, tabloid hacks are not all monsters. He told the Sun’s lawyer he suspected his contact had stolen the phone. He and the lawyers killed the story. He gave the phone back to the walk-in. Later the police arrested and cautioned her under the Theft Act, and returned the phone to its rightful owner.

That seemed to be that. The reporter moved on to another job as a foreign correspondent in the States. The petty thief had only a tiny mark on her criminal record that hardly anyone would know about. The celebrity continued to keep his sex life private.

It was as if nothing had happened, until three years later in 2012 the police arrested the reporter for possession of criminal property and a catch-all offence that could trap every investigative journalist — ‘computer misuse’ — a charge without a public interest defence. He lost his job and his new life in America. Like scores of other journalists and confidential sources — more now than ever before in British history — he is waiting to see if the Crown Prosecution Service will send him to the dock.

If it does, it will show how stupid Britain’s forces of law and order have become. I hear that the CPS is trying to keep the celeb’s name secret, but there is no guarantee that it can. If it fails, the state, which accuses the tabloids of invading the privacy of the famous, will be invading his privacy itself. The reporter, meanwhile, will face a full criminal hearing, even though the police let off the actual thief with a caution. In the 1990s, I published a collection of essays called Cruel Britannia on the early Blair years. I chose as my subtitle ‘Reports on the Sinister and the Preposterous’. What applied then, applies now — only doubly so.

Britain’s authorities are sinister because they are turning on fundamental liberties, without which a free society cannot function: freedom of speech, freedom of the press and the right to protest. They are preposterous because they are wasting their time and our money on crimes that turn out not to be crimes on closer examination. Instead of keeping a steady head, they pander to popular hysteria and round up despised minorities: left-wing demonstrators, tabloid journalists and the politically incorrect users of social media. It is as if the criminal justice system has become a vast job creation scheme for cops and briefs. Or perhaps the better comparison is with the Aztec gods, who needed a steady flow of sacrificial victims to satiate their hunger. It certainly feels that way when I talk to honest men and women caught in the law’s maw.

‘Don’t they have anything better to do?’ used to be the question when the police were caught wasting their own time. The surprising answer today is that often they do not.

Crime is falling across the developed world. Sociologists cannot say why. Tougher punishments do not explain the trend. The punitive United States has two million in custody, and has seen its crime rate collapse. But so have the soft-liberal states of northern Europe. The authors of the best-selling Freakonomics claimed that freely available abortion had led to poor women aborting boys, who would otherwise have grown up to be criminals. Their eugenic fantasy had no basis in fact either — crime rates were lower when abortion was illegal. The right’s warning that ‘the collapse of the family’ would lead to social breakdown has proved to be as false — crime has fallen as single parenthood has grown. The left’s warning that inequality and poverty will bring disorder on the streets has turned out to be nonsense too — the crime figures keep going down despite the worst recession in a century. Better car immobilisers, security cameras and burglar alarms are probably part of the explanation, as are an ageing population and more humane treatments for the mentally ill and disabled.

For whatever reason — and even the pacifying effects of unleaded petrol have been suggested — the developed world is going through a cultural change as dramatic as the shift in the mid-19th century when the Victorians rejected the licentiousness of the Georgians and embraced respectability. The ‘young people of today’, so often condemned, are less likely to get drunk or stoned than their parents were, and much less likely to burgle your home or rob you in the street. Saffy, Jennifer Saunders’s puritanical daughter in Absolutely Fabulous, is as much a sign of the times as a comic character.

There are two ways to respond to the news that crime has halved in England and Wales since 1995. The public could rejoice that last year we enjoyed the largest fall in violent crime in Europe over the last decade. A safer society is a society worth having, after all. For the police, however, a safer society is a clear and present danger. Crime may have halved since 1995, but police numbers are up: from 127,222 to 129,584 in 2012 in England and Wales; and from 14,323 in to 17,436 in Scotland. How can these officers justify their salaries and pensions, when so many are surplus to requirements? The answer the police have found is to criminalise behaviour that was never criminal in the past and should not be criminal now.

We will have to wait until the trials are over, but from what I am hearing the phone hacking cases stand a good chance of being remembered as the most vexatious litigation in English legal history. They are already the largest and most expensive police investigation ever. That on its own is an astonishing fact. Britain’s largest police investigation — costing £19.5 million as of June this year, the last month for which we have figures — was not into murder or paedophilia or terrorism but into journalism. Detectives have arrested more than 100 journalists and their sources to date. Only countries like Iran and Turkey arrest reporters in such number, and for this reason alone the Metropolitan Police and Crown Prosecution Service will be as much on trial as the defendants.

I urge you to keep your eyes open for two tricks they may have pulled when the hearings begin. Off the record, I am told that many reporters charged with paying for stories — of ‘procuring misconduct in public office’ as the archaic wording of the common law has it — will say, ‘Yes, I paid for information but the story I received was in the public interest.’ If they do, they will tell us that the authorities took advantage of an outbreak of moral hysteria — which, as Lord Macaulay noted, periodically make the British so ridiculous — to punish whistle-blowers and send a chilling message to all state servants that they will receive the same treatment if they speak out.

You should watch out too for cases so trivial and pointless that you wonder about the mentality of the prosecutor who approved them. A reporter I know has been kept on bail for months for an off-the-cuff remark he made in an email and because he worked near a man who was an alleged hacker. If they come to court, these prosecutions will send journalists rather than sources a message. ‘We can make your lives hell, for years,’ they will say. ‘Are you sure you want to go through all of that?’

Too few realise that the police have every-thing they need, because, to save his worthless skin, and the skin of his equally worthless son James, Rupert Murdoch handed over all the evidence, however flimsy, for detectives to use against his own journalists and supposedly confidential sources.

Despite promises from the Director of Public Prosecutions to the contrary, the web remains an equally profitable source of material for underemployed officers. Kent police, for instance, investigated their own youth commissioner — a luckless 17-year-old called Paris Brown — for making allegedly racist and homophobic tweets. In this, as in so many other investigations into ‘hate speech’, the fundamental principle of free societies was forgotten. It is not enough for the state to say that speech is hateful: it should have to show that the offending words would incite violence before our underemployed cops can investigate. If a religious fanatic is inciting a mob outside a gay bar, arrest him, of course. If he is expressing an obnoxious opinion, argue with him.

Just in case you are thinking it is only Sun reporters, ‘bigots’ and other traditional objects of leftish antipathy who are suffering, notice how the police boast of mass arrests at left-wing demonstrations and only months later admit sotto voce that they have made a mistake. The most notable climbdown came from protests against the G20 in 2009, when the Met had to accept that its arrests were unlawful. More often, they just quietly release innocent protestors without charge.

We should be enjoying a peace dividend as crime falls. We should be a happier country, freed from fear. Instead we are becoming a frightened and cautious people. The devil has found work for the police’s idle hands, and they are meddling with the freedoms that make democratic life worth living.