In 1910, the Liberal home secretary of the day declared that "the mood and temper of the public in regard to the treatment of crime and criminals is one of the most unfailing tests of the civilisation of any country."
That man was, of course, none other than Winston Spencer Churchill. He understood, profoundly, the power of rehabilitation, describing his "unfaltering faith that there is a treasure, if only you can find it in the heart of every person."
When Churchill spoke, however, there were just 20,000 people in jail in England and Wales. Now there are over 85,000 - an increase in prison numbers at six times the pace of our population growth.
More astoundingly, most of this increase has taken place since Margaret Thatcher left office. Ever since Michael Howard's 1993 "prison works" speech, which put an end to a comparatively enlightened period in criminal justice policy, both the Conservatives and Labour have competed to drive up the numbers of those behind bars - irrespective of the effectiveness of what was actually happening there.
The last government saw the quite extraordinary spectacle of Sadiq Khan, a fair-weather progressive, baiting Chris Grayling for a 'failure' to build more prisons.
There can be no other area of public policy, with the exception of the related issue of drugs reform, where establishment politicians so readily bang the drum for the exact opposite of any evidence-based solution. Our prisons clearly fail to rehabilitate: half of those released reoffend within a year, including six in ten of those on sentences of less than twelve months.
Liberal Democrats must lead the call for drastic and urgent action to reduce crime, protect victims more effectively, help criminals turn their lives around and protect taxpayers money: we must push for a Ministry of Justice target to halve the prison population by 2025.
Is this an unthinkably radical policy? Only if you think the incarceration rate seen under that famous woolly liberal Margaret Thatcher is unthinkable. Germany currently imprisons people at half our rate and experiences from Finland, which has managed a three-fold decrease in its prison population since the 1960s, show that change can happen.
Part of the reason our reoffending rate is so high, putting public safety at risk, is that our prisons are so overstretched that they are unable to deal with the complex reasons that lay at the heart of why individuals commit crime. A portion of the estimated £1.2billion savings which could be realised through a reduction in prison numbers should be invested in better resourced and more robust community sentences, including drug and alcohol treatment, more support for people with mental ill health, beneficial unpaid work and restorative justice. These have proven far more effective in turning people's lives around than locking people up for a short period, at great expense, and hoping for the best.
By creating more effective alternatives to prison for sentencers, they will be less likely to put people behind bars unnecessarily. To ensure a reduction in needless spells in prison, the Ministry of Justice should also introduce a presumption against short sentences, and require sentencers to explain themselves whenever they use a short sentence. Currently, there is political pressure in favour of the overuse of jail - the opposite should be the case.
During my time as a health minister, we made great strides towards dealing with criminals suffering from mental ill health. The roll out of the national liaison and diversion service - aimed at getting people who suffer mental ill health, who come into contact with the criminal justice system, into treatment - is world leading. It is a scandal of our time that there are so many people who are in prison largely because of their mental ill health or because they have a learning disability. Simply punishing without providing adequate treatment is wholly counterproductive. Of profound concern is the increase in the number of prisoners who take their own lives. There is an absolute imperative that this is effectively addressed.
We must take the same approach with children and young people who commit crime, treating them as vulnerable people first and foremost. We need a system that recognises that many of these young people themselves come from backgrounds of abuse, neglect and violence - and have not had a good start in life. Putting them in large institutions that differ in no real way from an adult prison is entirely the wrong approach. They are colleges of crime. For the small number of children and young people who truly need incarceration, we must revisit welfare-based approaches like small 'secure homes' that focus squarely on their complex welfare needs.
Finally, we must recognise that prison is often the source of more problems than it resolves (its effect on exacerbating problems of drug dependency and mental ill health, for instance, are well-documented). Perhaps most worrying, however, is that, according to a recent report by the former Head of the National Counter Terrorism Security Office, our oversized and poorly staffed jails are becoming breeding grounds for Islamic extremism. With more and more people behind bars, it is becoming harder for staff to monitor extremists. Rather than taking away our hard-won civil liberties, a far more effective means of combatting terrorism will be getting to grips with our overstretched prisons.
Liberal Democrats are at our best when acting as a voice for the voiceless. This includes both communities plagued by criminality - and those who have committed crime. It is my belief that the path to rebuilding our party lies in articulating a clear set of liberal principles in everything we do, so that whether or not people agree with us, they respect our motivations and know where we stand. Through this distinctiveness, we will be able to show millions of people who share our values that they belong in our movement.
We will never by afraid of radical evidence-based policies to improve people's lives and keep the public safe - and a rallying cry to reduce the prison population will be a key part of that.
Norman Lamb is the Lib Dem MP for North Norfolk, and is standing to be the next leader of the Liberal Democrat partySuggest a correction