Hello, Mr Straw, I’ve met you before,” said a prisoner in Garth Prison, in 2008. “In Brixton Prison, in 1998”.

This guy had spent 10 of the previous 14 years in jail. All the bravado his ilk show as young adults had gone. He was now sad and depressed. But when he left prison again, the chances were he’d be back on drugs and drink, back thieving and robbing.

Breaking this cycle is one of the biggest challenge the system faces.

Once is enough for many people who end up on the wrong side of the law. Crime is going down. What’s particularly welcome is that the number of youngsters who are “first-time entrants” into the criminal justice system is much reduced. But a single crime is one too many – especially if you are a victim.

And there’s a hard core of offenders who simply don’t get the point. The courts give them a second, then a third chance, with a community sentence. They take the mick. Offend again. The courts then lose patience and lock them up.

In 2010, a group of successful entrepreneurs came to see me while I was Justice Secretary to ask me to pilot a bright idea, to get people to invest in schemes to reform prisoners and ensure they stayed out of trouble.

The system has a fancy title “Social Impact Bonds”, but, in essence, it’s simple.

Foundations and trusts (or individuals) put their money into projects aimed at improving crime prevention and rehabilitation. The greater the reduction in reconvictions, the higher their return – up to a ceiling.

Below a certain rate, they don’t get their money back – it’s treated as a donation.

I agreed a pilot – for 3,000 short-term prisoners who’d be through Peterborough Prison – just before the 2010 Election. This was the first in the world.

Now a major international report wants to extend this approach. They say based on performance so far, investors in the Peterborough scheme should get their money back.

The charities and foundations benefit, the criminals now off drugs and crime benefit – and, above all, so do the law-abiding public.