Michael Gove’s tenure as Justice Secretary was always going to be about more than the not inconsiderable question of the Human Rights Act. My colleague Peter Hoskin wondered back in June whether he would – and could – bring the reforming zeal he showed on schools to the failing prison system. And the system is failing; as I argued earlier in the year, the shocking rates of reoffending ought to stir all those who care about crime, public spending and ruined lives – namely, all Conservatives – to action.

So it’s interesting to note that today Gove announces plans to sell off old prisons and build 9 replacements more suited to the modern age. The plan is based on a 2013 Policy Exchange report which argued that the development value of inner-city prison sites would fund their replacement elsewhere and allow the MoJ to save further money by avoiding the costs of running outdated institutions.

The Justice Secretary’s ambition to bring down the prison population sustainably, by improving rehabilitation rather than simply through softer sentencing, obviously requires facilities for that rehabilitation to be carried out. Cramped buildings where inmates need to be locked in their cells at times when they could be learning how to establish a law-abiding life on the outside are not up to the job.

Making the sums add up will be crucial. We’ve yet to find out the full list of sites which are to be sold and the specifications for those to be opened – it’s certainly the case that a lot of money could be made from selling a site for housing in, say, Brixton but the question of how much the prisons will cost to build is yet to be answered.

And there are also logistical questions. One principle of the prison system is meant to be that inmates are normally jailed close enough to their home for family members to visit, so it won’t be a question of simply looking for the cheapest location.

Once those hurdles are cleared, the principle is a sound one. If Gove’s legacy is less reoffending, less money spent on warehousing convicts, fewer crimes and fewer wasted lives then it will be his second gift to society. He can do it – when he laid out the scale of his ambitions in school reform, people dismissed it as talk but he delivered nonetheless. All power to his elbow.