Closing all NHS long-stay hospitals for learning-disabled people in England was a historic, if tortuous, achievement. But as Panorama has shown, some people are now sent to equivalent units run by private companies which, like Winterbourne View, masquerade as short-term assessment and treatment centres. There was nothing short-term about the placements in the programme, nor was there much evidence of assessment and treatment.

There was, however, plenty of evidence of the kind of physical and verbal abuse that was all too common in NHS units such as Orchard Hill in Sutton, south London, which was the last hospital of its kind to close, in 2009, after having itself been exposed two years earlier for a regime of physical and sexual abuse of people who lived there.

The link between Winterbourne View and Orchard Hill, and with an earlier NHS scandal in Cornwall, is made in today's letter to David Cameron. The learning from past inquiries "appears to have been forgotten", say the signatories, who include former government policy advisers Rob Greig and Jim Mansell, "in part because of the continual reorganisation of public services".

The letter calls for the phasing out over two years of placements in private hospitals, with commissioners of care "prevented" from making any future such arrangements. In the meantime, it says, inspectors should ensure a "dramatic" reduction in use of restraint techniques in the hospitals and an opening-up of their culture. All people placed in the hospitals should be guaranteed independent advocacy.

Forestalling the inevitable ministerial response that these are matters for local decision-making, the signatories say: "The underpinning issue is one of the overall service and system design hence the need for government to take a lead."

Handily, powerful evidence has emerged this week to lend weight to the letter. Publishing an evaluation of how the last Orchard Hill residents have fared since they moved to live with support in the community, Sutton council says they are happier, fitter and enjoying far greater independence, dignity and control over their lives. Oh and their care and support costs are almost a third less.

Bear in mind that these last 39 residents of Orchard Hill were considered the most dependent and challenging people placed there. One woman had a vocabulary of only 40 words. Today, she has command of one exceeding 1,400. The evaluation, carried out by the University of Chester, found "significant" improvement in the group's quality of life within just six months of leaving the hospital. Within 18 months, it had risen by a third.

"People are making the most remarkable progress, beyond all expectations," says Colin Stears, the council's executive member for adult social services. "Returning people to their local communities by making supported living a reality has restored the human rights of people with learning disabilities, many of whom have very complex needs."

Cameron, whose disabled son died two years ago, is said to have been distressed by the Panorama programme. He should need no further persuasion to stop the worst of old-style NHS institutional care, something we thought we had left behind, being replicated by the private sector at places like Winterbourne View.