I have interviewed abused women, bereaved parents, torture victims and girls in the captivity of jihadis.

I have seen fields strewn with dead bodies, hospitals flooded with ebola victims and towns crushed by aerial bombing.

But nothing has felt so traumatic as my investigation for this newspaper of people with autism and learning disabilities being locked up in cruel and destructive conditions across Britain.

It is heartbreaking as I listen to parents, often in tears and sometimes silenced by court orders, tell of children torn from families and sent to secretive units that can devastate lives for ever.

It is heartbreaking as I listen to parents, often in tears and sometimes silenced by court orders, tell of children torn from families and sent to secretive units that can devastate lives for ever (stock image)

Perhaps it strikes home so hard because my own daughter has profound learning disabilities, so I understand what it is like to struggle against a powerful system that pretends to be helping, and to feel alienated from wider society.

Perhaps it is despair that there is so little sympathy for people whose only offence is to see the world differently. Or simply the discovery of human rights abuses taking place in heart of my nation with grim deeds we thought banished to the dark past.

Last month I was in Belgium examining controversies over permitting people with extreme mental health problems to end their lives.

I was stunned after asking a young scientist what led her to go through this process to win the right to euthanasia. She said it was the trauma of being locked up for five years as an autistic teenager in an adult psychiatric unit.

If you understand anything about autism and learning disabilities, then you can appreciate how this smart but troubled woman had reached this tragic point after years of forced sedation and frequent seclusion.

Such people can need order, routine and control in their lives. They might struggle with sensory overload such as bright lights, loud noises and crowded places.

Grim deeds we thought had been banished to the dark past

If they have one type of autism, called pathological demand avoidance – traits seen in the awful case of Bethany, one of the first autistic teenagers I reported on, who was locked in seclusion and fed through a hatch – they may need coaxing rather than coercion. So when they have anxieties, it is hard to think of anything worse than confining them in chaotic places filled with troubled psychiatric patients and where staff often lack correct training.

Then, when these people go to pieces, they lock them up in tiny cells and treat them like dangerous animals.

Their families also suffer. Many disintegrate under the immense stress of seeing their beloved children suffer systemic abuse or forcibly sedated into zombies.

There is a clear pattern. Parents seek help as children hit adolescence and become bigger. They trust experts who say it will just take a few weeks in an assessment and treatment unit. Then the teenagers and young adults are snared for years.

Health Secretary Matt Hancock promised to act after reading my reports – then pathetically ordered another limited review that does not report finally until 2020

Once inside, many are frequently moved – sometimes in cages – far away.

One mother told me she spends £250 and two days making each 800-mile round-trip to visit her son for two hours.

Bear in mind that autism and learning disabilities are not conditions that can be cured. These are simply people with alternative needs, outlooks and perceptions who are being detained without dignity or justice.

Men and women handle incarceration differently. Men can become more angry and aggressive. Women, often placed with patients who are self-harming or suffering eating disorders, start mimicking such behaviour to fit in. Such incarceration is like a spiral of cruelty.

It locks innocent people in unsuitable places that intensify mental stresses, which then make it harder for them to win freedom.

This is all bad enough. But it gets worse. For there is a whiff of corruption emerging from this system as rapacious private firms muscle in on the system, raking off vast profits while having the power to determine if people can escape their clutches.

Multinationals, hedge funds and private equity groups are buying up psychiatric units holding these people and opening new centres – yet Ministers have repeatedly promised to empty them since the Winterbourne View abuse scandal in 2011. No wonder: they earn fees of up to £2,007 a day per patient while paying support staff scarcely more than minimum wage. So we have the sickening sight of the Priory Group owner giving £8.2 million to its sacked US boss while paying £8.50 an hour to carers.

This money comes from the NHS, although it is often far cheaper, more effective and definitely more humane to provide proper community support. But this comes from cash-strapped councils, so many prefer to dump the problem on the NHS. Children’s mental health services are also badly underfunded, so some also shift problems by sectioning challenging teenagers. One such distressing case came to my attention last week when I discovered that a nine-year-old boy with autism was nearly sent to an adult secure unit recently. ‘Everyone was saying they could not cope,’ said Michael Richards, a senior social worker in Berkshire. ‘But the last resort should not have been a psychiatric hospital.’

With the help of experts, tiny changes at home – such as fixing meal times and shifting the boy into his own bedroom – ensured that after three months his behaviour improved and medication stopped. ‘Small things can be very meaningful for an autistic person but there is systemic failure in many places,’ said Mr Richards.

Yet, once again, for all the lofty talk of transforming care, politicians have kicked this into touch. Health Secretary Matt Hancock promised to act after reading my reports – then pathetically ordered another limited review that does not report finally until 2020.

Meanwhile, MPs debated a bill last week regarding treatment of people who lack capacity to give consent that makes it easier to hold people for longer periods while doing little to stop conflicts of interest for private firms with power to deprive citizens of their liberty. There are many causes of this crisis, from incompetence and complacency through to a disturbing lack of compassion. But hidden away behind locked doors, barbarism is being inflicted on people with autism and learning disabilities.

At this time of family celebration, remember these traumatised citizens and families ripped apart by the state under the guise of ‘care’. Then think of that famous saying that you measure a nation’s worth by how it treats its weakest members – and ask what this scandal tells us about 21st Century Britain?