YOU, dear reader, may think that if the police catch more criminals, and they then serve longer prison sentences, fewer crimes are likely to be committed.

I have long taken the same view.

It does seem obvious, doesn’t it?

You and I are, however, prejudiced simpletons in the eyes of many “experts”, including quite a body of academic criminologists.

We’ve got it wrong, they say – on the grounds that the link between crime and punishment is unproven.

I used to invite those who took this view (echoed in some of our fancier national newspapers) to come with me to visit families whose area had been run ragged by burglars, thieves, and bullies.

Ask the victims which made the difference – putting the serial offenders back on probation (again), or locking them up in prison.

I also suggested that my critics might hang around Blackburn Magistrates’ Court (or any other court), and listen to the offenders’ friends when sentence has been pronounced.

The persistent, hardened criminals aren’t in any doubt themselves.

They call a non-custodial sentence being “let off”.

Now, at long last, there’s some serious, respectable evidence from academic criminologists to tell you, and I (and every police officer) what we have long known – that the greater the chance of detection, the longer the prison sentence, the less crime there is likely to be.

The evidence comes from the University of Birmingham, and has just been published by the think tank, Civitas.

Their estimates “indicate that even a relatively small change in sentencing can achieve a visible reduction in the number of recorded crimes”; and “with respect to policing, the evidence is unequivocal: more detection is associated with substantial reductions in crime”.

The research does not suggest that first-time offenders should all be locked up; nor have I ever believed that.

Probation and other non-custodial sentences can be very effective for this group.

But for people who’ve chosen to make a career of crime, getting tough does work.

There are 40% more prisoners than there were 15 years ago, and around 40% less crime. QED?