I didn't watch the documentary but I did hear the discussion and phone in on the radio yesterday morning
In the late 1970's, I worked on a project where we set up packages as an alternative for custody for so called recidivists. The prison population was much smaller, staff to prisoner ratio much higher and drug use in prisons nothing like it is now. It was the case then, as it remains, that prison where individuals are locked up 23 hours a day isn't effective. We imprison more people than other European countries, our recidivist rate is high.
We need to stop this austerity approach to justice, social care, education, health etc and invest in our people. Sorry to irritate some folks but we need to take more notice of 'experts' those who work in those areas, look at the research. None of those things support the continuing slash and burn approach to essential public services.