I remember very clearly my reaction when I first heard of the idea that prisons might be run by private companies: ‘some bright young thing in a think tank, wanting to show just how far outside the box he can think – of course, it won't survive ten minutes contact with reality’.

Twenty-five years later, the private sector runs sixteen prisons, four Secure Training Centres and nine Immigration Removal Centres, together with all prisoner escorts and all electronic tagging, at a total cost nearing £1 billion a year.

And it formed the central part of my own career. As Finance Director (FD) of HM Prison Service (HMPS) in the late 1990s, I was responsible for running competitions, and awarding and managing contracts, and also for improving the efficiency of the public sector. I then headed up competition policy in the new National Offender Management Service (NOMS). I later worked for two companies – one competing with HMPS to run prisons, the other in partnership with HMPS, competing together against the private sector. So I have seen the issues from both sides of the fence and, indeed, on it. Whether that makes me an objective observer is for others to judge.

I wrote this book because this has been a long-running, controversial and important experiment in public policy, and the time now seems right to review how well or how badly it has worked.

Private provision of public services is a major political issue in this country, which has gone much further in prisons here than even the United States. And prisons have been one of the longest running – and most sensitive and most controversial – experiments in contracting out public services, and also one of the most complete.

Yet there has been no comprehensive and objective review of the benefits or otherwise of competition in this country, or how well effectively it operated. Much commentary has been from prepared positions, whether of ideology or self-interest or both. (My own position, to be clear, is neutral between sectors: I am interested in what gets the best result for the money available.)

And some aspects, particularly comparative cost, competition policy, the significance of different approaches to procurement, and the impact on competition on the public sector, have not been satisfactorily examined.