Rosemary Severin (nee Montefiore) was, and is, an Australian. Hailing from the south-east Queensland town of Stanthorpe, she travelled with fellow young nurses to work in London in 1952. Soon she was on a break in the Austrian Alps when she met a young German medical student, Berthold Severin, on a dance floor.

Six decades later, their son is telling their story while grazing on entrees of satay chicken and spring rolls at a southern-style Thai restaurant, Caysorn, in Sydney's Haymarket. It is a short stroll from here to the office where 58-year-old Peter Severin, the Corrective Services Commissioner since 2012, administers the state's jails.

Severin adds some context to his mother's early experience in Europe. So soon after World War II, a young woman had "a certain view of Germans that was not unreasonable, I guess. To this day she talks about her first night in a German hotel. There must have been a bit of an argument happening next door, but she was very scared about the language, the accents. It was quite intimidating for her.

"But obviously love was stronger than prejudices. They persevered."

Rosemary married Berthold and they had their first child, Peter, in 1956. They settled in Emmerthal, a village outside Hamelin, where Berthold and his father, also a doctor, shared a country practice. There was some expectation that Peter would follow them into medicine but the younger Severin would have other ideas.

At 17, he was a member of a local youth group that visited inmates, supported by Hamelin's reformist prison chief.

"After the Second World War, my generation grew up with a deep sense of responsibility for what happened," Severin says. "Even though we weren't there during the Nazi regime, it was obviously abhorrent and game-changing on a world scale. Growing up with that deep sense of responsibility certainly instilled a sense of social purpose in me."

Severin studied social work at the local university, but with the express intention of becoming a prison officer.

"Maybe that's where some of the misconception comes from now – that I was just a social worker – because in Australia I didn't start as a prison officer. But in Germany I did."

Severin does not volunteer the name of the most notable source of this "misconception", the radio 2GB shock-jock Ray Hadley. In September, after riots at the Goulburn maximum-security jail, Hadley told his listeners: "The bloke's a dill."

He reckoned Severin was a laughing stock among prison officers, a mere "public servant" and "a social reformer who wants to sit in the lotus position". Hadley complained that the former NSW attorney-general, Greg Smith, had replaced his good mate, the "tough old nut" Ron Woodham, with Severin because the minister wanted a reformer as the boss of prisons.

"A bloke who knows nothing about what it's like to be a prison officer," Hadley claimed. "Absolutely nothing. Absolutely nothing. Despite the fact he's worked in prisons in Queensland and South Australia, has he ever faced an angry man in a prison yard? The answer is no, no and no."

The answer, rather, is yes, yes and yes. Not that Severin puts it this way. He's far too mild-mannered and clever to enter a slanging match with Hadley, but Severin indeed started his career as a prison officer in Hamelin. He was king-hit by an inmate in his first two years. He persevered in the jail's tough remand section for eight years.

He was among the first officers to respond to a riot by more than a dozen inmates who ignited fires while two of them climbed atop wheelie bins and fashioned nooses to hang themselves. They had to be talked down. Another time, a young mentally disturbed prisoner set himself ablaze. Severin was among the officers who retrieved his horrifically scorched body.

"That cuts deep," he says. He praises the work of NSW prison staff but does not elaborate on Hadley's claims, other than to say: "It's not about being tough or weak. It's about being smart …"

Severin's choice for our main course arrives. It is kua kling, spicy red curry with pork. It is extremely hot, which  seems to trouble Severin less than it does his lunch companion, while  the 9^th Island pinot grigio only serves to distribute the heat evenly over the palate. A milder chicken curry arrives and the chokos swimming in its sauce provide some balm to a throbbing tongue.

Severin continues: "I would never support anything that compromised community or prison safety, but the sheer call for being tough is quite ignorant of all the dynamics that make up a prison system."

. Severin was always a dual citizen, but first visited Australia in 1978, when he was 21, deciding to settle here a decade later  at the age of 32.

At first he thought: "New country, new language, new opportunities." He would get out of jails. "But Queensland had just gone through huge reform with the Kennedy review of corrective services."

He started as a correctional counsellor at the new Sir David Longland Correctional Centre in Brisbane. Eighteen months later, he was poached by Australia's first privately run prison, but soon was lured back to join the commissioning team for a new remand centre. In 1993 he became general manager of the Brisbane Women's Correctional Centre.

"I once visited a prison in the United States, a men's and women's prison in the one complex." A corridor of about 20 metres separated the two sections. "We walk past the men, a single line. They don't say anything. They don't look you in the eyes. Then the manager says, 'Watch this.' We open the door to the women's section, and it is like a bee hive. Everyone is all over the place, talking. And the manager says: 'You know, in our trade, when the men become really noisy, you need to be on alert. And when the women stop being noisy, you have to be on alert.' "

Severin rose to become the deputy director-general of corrections in Queensland in 2001 and in 2003 was lured to lead South Australia's prisons system, where his nine years as chief executive were marked by a significant decline in the rate of inmates re-offending – "from the high 30s to high 20s" in percentage terms.

"To me, it's a fundamental philosophy. Prisons should not be out of sight, out of mind, a service at the end of the conveyer belt on the fringe of society. I believe if you give a person the ability to read and write and the ability to be marketable in their skills, and to find some employment and strong social connections, that is a huge advantage in stopping re-offending."

In NSW, Severin says, he puts  the focus on evidence-based programs that address violence, domestic violence and drug and alcohol abuse. "But, no, we don't let people out just because they've behaved well in jail, 'You've been a good boy. Off you go.' It doesn't work like that. We're looking at their risk of re-offending. We're measuring that."

For those who measure up, state-run half-way houses deemed to have failed have been shut. Instead, non-government agencies manage the transition of released inmates – accommodation, connections to the community, links to potential employers. The Baird government has just announced a funding rise of more than $3 million to $8.4 million over three years and the program will reach 700 released inmates a year, up from 135.

Severin points out that Corrective Services already supervises 16,500 offenders in the community, 4000 more than are behind bars in NSW. "And the evidence is that this works." He cites the findings of Don Weatherburn, the director of the NSW Bureau of Crime Statistics and Research, that supervised offenders are less likely to re-offend than ex-prisoners not under supervision.

Weatherburn says he has found  Severin  "refreshingly honest and apolitical".  It was Weatherburn who reported in April that the NSW prison population had reached a historic peak of 10,825. A significant rise had coincided, ironically, with a big fall in crime since 2000. But fewer crimes allowed the same number of police to better target their investigations – to offences that were more likely to result in prison terms.

Then the wheel turned again. Police suddenly reduced the number of bail court attendance notices they issued, meaning more accused people remained free pending their court cases. It led to a big fall in prisoners on remand and by September the total prison population had dropped to 10,426.

Severin has no control over the incoming. He says he cannot put up a "no vacancy" sign.

But he can influence the number of prisoners who re-offend. Prisons, he says, must strive to be places of redemption and hope.

Even for the thrill killers of teacher Janine Balding? The United Nations Human Rights Committee has found that the life sentences handed to two boys, who were 14 and 16 when they joined in her gang rape and murder in 1988, were "inhuman and degrading" and that there should be some prospect for their release if they are rehabilitated.

Severin will not comment on the particular case, but he says: "I firmly believe there are some people who should never be released." He adds, however: "We need to manage a system that doesn't turn off every light at the end of the tunnel."

Some of that light, he says, must shine for indigenous prisoners, who represent less than 3 per cent of the NSW population but a quarter of the state's prisoners. "Indigenous prison numbers are growing nationally, not falling, so we have gone backwards."

: From early 2015, the Kariong Correctional Centre on the Central Coast will specialise in stopping re-offending by young Aboriginal males.  "It will target short-term Aboriginal prisoners for the first time. For too long we've said, 'Unless you serve a sufficient period of time in jail, there's very little we can do for you. You get in, you churn through, you get out."' And too often get in again.

Health teams are  also focusing on the needs of prisoners with a  history of mental illness, who make up 49 per cent of all inmates. Severin concedes they may only be "scratching the surface … but we have come a long way".

There will always be challenges. "When I started out in this game a long, long time ago – when I was a smoker – a friend of mine said: 'Corrections is like trying to smoke under a running shower.' And in many ways that's true. I've simply given up smoking, I guess."

He has no plan to give up corrections.

Life and times

1956: Born, Hanover

1983: Bachelor of Social Work, University of Applied Science, Braunschweig

1980 - 1988:  Correctional Officer, various ranks, Lower Saxony Justice Department, Germany

1988: Moves to Australia and joins Queensland Corrective Services Commission

1990-91: Case Manager, Borallon Correctional Centre, Corrections Corporation of Australia

1993-96: General Manager, Brisbane Women's Correctional Centre

2001-03: Deputy Director-General, Department of Corrective Services, Queensland

2003-2012: Chief Executive, Department for Correctional Services, South Australia

2008: Master of Public Administration, Griffith University

2012 - present: Commissioner, Corrective Services NSW