I'm sitting in Oslo having lunch with the director general of the Norwegian prison service – Kristin Bolgen Bronebakk – and we are discussing "Scandinavian exceptionalism". In other words, why is it that Finland, Sweden and Norway in particular, have much lower rates of imprisonment than other European countries? For example, whereas Scotland has over 7,000 inmates being held in 16 jails, Norway with a similar population has just over 3,500 prisoners, held in 50 prisons – a prison population rate of 75 for Norway but 142 for Scotland.

I point out to Bronebakk that Bastoy Prison – a minimum security facility located on Bastoy Island, south of Oslo – would probably feature on the front page of our tabloid press every day given that the 115 prisoners held there are encouraged to engage in "horseback riding, fishing, tennis and cross-country skiing" during their leisure time. One of her staff overhearing this observation laughs and points out that Michael Moore, the American film director, had wanted to feature the prison in one of his documentaries, but thought that absolutely no one would believe that he was really filming in a jail.

Bronebakk has clearly read the biography that the Commission on English Prisons Today has sent to Norway about me and the other visiting commissioners, and she asks about my academic work with serial killers. Being polite, I say that I can't think of a Norwegian serial killer, but Bronebakk says they did have one – Arnfinn Nesset. Nesset was a nurse convicted in 1983 of poisoning 22 patients with Curacit – a muscle relaxant – at a geriatric institution in Orkdal, although he was suspected of having killed several more before being caught. I suggest that murdering medics is quite a common phenomenon and that our most recent serial killer, Colin Norris, was also a nurse who targeted the elderly, but then Bronebakk takes me by surprise again.

"Of course," she says, "we released Nesset in 2004." And indeed they had, given that the maximum sentence that anyone can serve in Norway is 21 years – or less than a year for each of his victims in Nesset's case.

But are there lessons for us to learn from this Scandinavian exceptionalism – given that we would never countenance the breathtaking range of activities that prisoners can become involved in or their relaxed attitude towards the release of serial killers? The answer is of course there are.

In Norway, prisons and imprisonment are not party political issues and so do not, by and large, come to public attention at all. Prisoners remain "citizens" and so still vote, have access to the internet, work, go to school and even make appointments to see journalists. And when there are scandals – such as when a prisoner on home leave murdered a young woman and drove around with her body in the boot of his car 18 months ago – the penal system is robust enough and the public debate rational enough to see this as a tragedy rather than the signal for root and branch change.

Later, discussing all of this with two of the leading lights of European prison reform – Professors Nils Christie and Thomas Mathiesen – they both reflect on what has allowed Norway to keep its prison population low and to generate such public support for this approach. Christie suggests that having a functioning welfare state has done a great deal, for this makes it difficult to create "social distance", so that each person feels connected to everyone else and therefore no one gets scapegoated for the troubles that occur. So, too, Mathiesen believes that the low prison numbers reflect a "moderate social system" in Norway, and that the only real danger is "excess" and the growing divide between those who have and those who have not.

I liked that word "moderate". After all, when we are all now beginning to see what excesses in eating, drinking, smoking can do to our lifestyles, and more immediately what gross excess in profit-making among our banks has done to the economy, isn't it about time we employed moderation more generally and specifically to the excesses of prison numbers?