If you want a picture of where Conservatives of all stripes are taking Britain, picture this.

A Roma woman, "Tanja", whose family arrived in Britain illegally, is in a room of the Yarl's Wood immigration removal centre, a block of bland modern buildings in the Bedfordshire countryside surrounded with barbed wire.

According to Tanja's account, a male guard locks the door. He pulls out his earpiece, perhaps to make sure he is not disturbed, and after some initial touching, he pushes his penis in her face. He laughs when he ejaculates in her mouth – so confident is he that he can escape punishment. As Mark Townsend reports in today's Observer, her allegations are not exceptional. One officer is alleged to have had sexual contact with four women. And there may be others we know nothing about.

Put yourself in Tanja's shoes and you will understand why something like this might happen. Take an isolated young woman, locked up in a detention centre, run for the British state by Serco, a private company that has built its profits by taking over public services. The corporate guards confine her and can punish her. One starts thrusting himself on her. What does she do? She could think that she has to go along with him or he'll put her on the next plane out. Or she could believe that if she does what she is told she will be in a relationship with an Englishman and that somehow this "affair" (if that is not too romantic a word) will allow her to stay in the country.

Either way, you might imagine that all targets of sexual predators agree on one point: they fear that, if they complain, deportation will follow. They may not be wholly deluded. Tanja was apparently targeted by three of Serco's creeps. A UK Border Agency investigation found that the three officers behaved unprofessionally in having sexual contact with Tanja. Police are examining a complaint that some of it was non-consensual.

The increasingly privatised criminal justice system has an interest in covering up mistreatment. I don't want to join the Pavlovian chants of "public good/private bad". The public sector is more than capable of hiding its vices, as the police and National Health Service demonstrate with dispiriting regularity. But although a scandal can destroy careers of individual public servants, it will not destroy the institution they serve. Whatever happens, the Metropolitan Police will still police London.

By contrast, scandal poses an existential threat to private corporations. If the complaints grow too loud, they can lose a contract. If they lose too many, they will go out of business.

Optimistic promoters of privatisation believe that the threat of bankruptcy is a market discipline that forces firms to meet higher standards than the sluggish public sector can attain. They have not grasped that the parasitic version of state capitalism Britain has developed is just as likely to regard secrecy as an essential self-defence mechanism. The officers at Yarl's Wood were not driven by market forces to offer a better service.

As for our leaders, can you imagine David Cameron, Theresa May or Chris Grayling giving thunderous speeches on the need to uphold decent standards in publicly funded institutions? Instead of announcing that they are willing to protect the vulnerable, they thunder that legal aid for poor claimants is a swindle that allows fat cat lawyers to get rich at the taxpayers' expense. Instead of ordering inquiries, they manipulate the law to stop the judiciary reviewing abuses of power by the likes of detention centre guards.

Chris Grayling, to take an asinine example, claimed last week that the courts have been taken over by left-wing agitators. Among their number our ignorant justice secretary includes the shire Tories who oppose HS2 and admirers of the Plantagenets who want a public consultation on where to bury the remains of Richard III, as if a nostalgic affection for the House of York were a leftwing cause.

We would not have published a word about Yarl's Wood were it not for the heroic efforts of Harriet Wistrich, the best feminist lawyer I know. But she will not be able to carry on bringing cases like these to the public's attention for much longer.

The legal aid cuts are not directed against fat cat lawyers, who continue to make their fortunes in the City, but against solicitors such as her, who do well if they make £40,000 a year. More seriously, they are directed against their clients.

As of this year, poor litigants, who could once take cases to court about their employment, their children's education, personal injury, clinical negligence, debt and housing no longer can. On matters of vital interest to them – and to wider society – they are beyond the rule of law.

The denial of access to justice falls with particularly severity on the state's detainees. The government will soon remove legal aid from prisoners who claim that their captors have mistreated them. As for the immigrant women, they will fail a new residency test and be denied access to justice too.

Wise politicians understand that the further they climb up the hierarchy, the less they know about the behaviour of public servants. They welcome challenges, not least because they warn them about the failures of the bureaucracy they are meant to control.

Coalition ministers, by contrast, abhor scrutiny. They don't want to know and don't want you to know either. They are using the Leveson report to limit press scrutiny and restrictions on litigation and expenditure to limit judicial scrutiny. They get away with it because the authoritarian left cheers them on when they attack freedom of the press and the authoritarian right cheers them on when they attack equality before the law.

No one is going to punish ministers. There are few votes in defending legal aid and none in defending public money going to that most despised group: illegal immigrants awaiting deportation. Even Observer readers may not want to hear about them and would much prefer to see a piece on Miley Cyrus. If so, don't worry. By this time next year, the sources for stories like ours on the women of Yarl's Wood will have disappeared. It will be as if they don't exist.

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