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.
By and large our politicians do work hard (although there are well-publicised exceptions!); something we tend to overlook when criticising them. And whilst Knauf reveals the human side to Cullen, it is his political legacy that he will be remembered for - and that legacy will not be remembered fondly by Keeping Stock. Knauf also touches on Cullen's crankiness, and he will of course be remembered for some infamous jibes which were caught on camera.
And whither now for Labour? Is Cullen the "glue" that has been holding the ship together since the election? We believe that he is, and from that perspective, Labour will miss Cullen far more than they miss Helen Clark.