Michael Cullen retires from Parliament this week. And with his approaching 30 years of service, there should be no shortage of commentators available to reflect on his legacy and his contribution.

As someone who served as his press secretary and speechwriter in only his last 12 months as a minister, I should probably leave it to others to speculate on the durability of the Superannuation Fund, KiwiSaver, Working for Families and his transformation of the Treaty Settlements process.

For what it's worth (and with as much personal bias aside as possible), I believe it is a hard ask to point to another Western social democrat of his generation who has left a larger imprint on their domestic policy landscape.

What my experience with Michael Cullen does grant me is a privileged perspective on the personality and temperament of a man who was often polarising, even when held in wide respect.

For many in the public, reconciling the man seen visibly angry in a controversially broadcast exchange with Guyon Espiner with the man visibly moved at the signing of the Central North Island forestry settlement is not an easy task.

How do you make sense of the formidable policy mind who amazed senior officials when he designed the expansion of KiwiSaver on a couple of sides of A5 (complete with costings) with the infuriated figure who labelled John Key a "rich prick"?

His image over nine years as Helen Clark's deputy was one of contradiction and one that contrasted greatly with his leader's consistency in the role of the pragmatic, decisive Prime Minister.

But those of us who have been lucky enough to work with Michael, even for short periods, know that there is a straight line through his personality that enabled him to steer Labour's policy ship for well over a decade, and that made him refuse to take simple steps that would have broadened his public appeal.

Let's look at the caricature of Michael painted by his enemies: the dangerously thrifty (or was it profligate?), overly clever Finance Minister who refused to cut taxes out of some deep-rooted class envy.

That is what political opponents - for better or worse - do to their enemies. They paint their desired image, and try to nurture its place in the popular imagination.

But for a man who came of age at a time when your performance in the debating chamber determined a large part of your political fortune - and when that score would leave him firmly in control of his own political destiny - Michael was never willing to play by the PR rulebook that would have helped him throw off this ridiculous sense of who he was.

Too often, in fact, he took the bait of journalists, and stepped right into their caricatures. You can debate the merits of talented reporters playing a game to see who can get the best rise out of a minister, but if you're the minister in question, not rising to it at all is surely the best strategy.

But it was the same refusal to play by the PR rules that now leaves Dr Cullen a true giant of New Zealand politics. The "initiative-itis" suffered by so many politicians around the world never affected him.

Policy made for a good night on TV was rightly viewed by him as policy that had no place in government. His mantra was to keep an eye on the long-term - look over the horizon - plan for uncertainty - and go after the big challenges.

And from a personal perspective, it was being infected by this philosophy that was my greatest reward from a year with Michael. He turned an unapologetic, 25-year-old political junkie into someone who still loves the game, but now knows what the real prizes are.

And he also taught all of us who worked for him to keep the human aspect of political endeavours alive in all we do. When he called his wife throughout the day to ask what she was doing or to share a laugh about an on-air scrap he had with Sean Plunket, we were reminded that we shouldn't let our ambitions overshadow our relationships and families.

When he admitted to shedding a few tears when he feared a foreshore and seabed negotiation might collapse after years of work (later saved), he taught us about investing personally and emotionally in what we did.

And when at 63 he complained about his regular illnesses and chronic fight with sleeplessness and yet still delivered virtuoso performances in policy meetings and at question time, he left an office filled with twenty- and thirtysomethings in amazement.

Michael Cullen is known to all - even his enemies - as a man who worked tirelessly to better the fortune of New Zealanders.

As someone who briefly got to know him as the boss who was always calm and generous with his staff, I feel very fortunate.

The House of Representatives loses its true leader this week - and it's difficult to imagine it getting another like him anytime soon.

* Jason Knauf is now London-based, attending the London School of Economics and working as a spokesman in the British Treasury.