Sir Peter Gluckman, the Prime Minister's chief science adviser and our most famous living scientist, has a reputation for not suffering fools (and he will regard that "most famous" as extremely foolish, while possibly not minding it too much). He must have been in a good mood the day I saw him because he suffered my foolishness with gruff good grace.

I didn't know what to call him: Sir Peter or Professor Gluckman. I noticed that his PA called him Peter, so perhaps he's not as impossible as he is sometimes portrayed to be.

He said, "Peter would be fine. You know, titles are nice things to have. One would be being inappropriately modest not to say: 'It's a nice thing to have."'

A colleague of mine once interviewed him and wrote that he treated him, tetchily, like his secretary. I reminded him of this, which elicited an uncharacteristic silence. Then he said, "What did that mean?" It meant that he doesn't enjoy being interrupted. "Well! I can't remember. I don't know. I mean, you guys have an annoying habit of interrupting trains of thought and ..." Do we? I interrupted. "And sometimes not allowing us to finish what we're trying to say. Yes, you do!" he said, mock glaring.

He was nice as pie to me. A plum pie, perhaps: the tart kind you eat warily, watching out for stones.

It is part of his job to relate well to the media. He is, I suggested, good with the media, to a point. He said,"You're who's obsessed with whether I'm good with the media or not. I don't care."

Doesn't he? I wasn't quite sure. "Well, I do care to the extent that my role now is to make sure that the media effectively transmits knowledge about science well." Quite. "And if you're asking me about the personal side of it, you guys have praised me, you've damned me, you've done everything under the sun! Ha, ha."

He can give a very good appearance of tetchiness, although this is rather undermined by the obvious glee with which such a performance is delivered (and by that "ha, ha"). He can't quite disguise, and doesn't try terribly hard to, that he thinks most journalists are a bit thick, scientifically speaking at least. That's if he has given even that much thought to the subject of journalists. He would no doubt say that me even wondering about what he thinks of journalists is proof of my obsession.

I'll own to one: getting hold of him. I first tried four months ago, when he'd been in the role for a year. Various appointments have been made and cancelled. He is a very, very busy man and a bugger to get hold of. He said, "Well, it's been unfortunate timing," by which he meant: not for him.

He has, according to me, an odd relationship with the media. He is said to be science-savvy as well as media-savvy. He knows the value of a headline. This wasn't a criticism; getting headlines is his job. He said he doesn't "go looking for them ... On the other hand, I have to make myself accessible. It comes with the turf when you're a dean of the medical school [at the University of Auckland] and you set up a research institute [The Liggins Institute] ... Phew!" Then he said, confidingly, "I'm actually a very private person." I don't know what that means. "Well, I'm not a social butterfly. We don't engage in a large social network. I mean, I'm not a recluse or anything like that but I'm quite comfortable having a bit of a quiet time. My wife spends my life saying, 'You don't engage in small talk'."

I asked about his spiritual life. "I have a cultural life." He goes to synagogue "aah, very occasionally". He and his wife, Judy, "have a kosher home". He's "not sure" if he believes in God. "I mean, it's an interesting thing. Theology is not very important to most Jews. I'm a rationalist at heart." This is his private life. "Yeah. I mean, it's why I'm hesitant about even answering this question. It is frankly none of your business ..."

Is he tetchy? He's certainly blunt. "If you think something's bullshit, say so." Most people, in interviews, if they don't want to talk about something, say, politely, "I'd rather not talk about that." Most people at the end of interviews say something pleasant. He just ... goes. Which is to say he makes not the slightest effort to charm, and you either like him for that or you don't. I happened to enjoy him, but I can see why he can come across as impossible, or arrogant.

He does have this very public role and the profile that goes with it. I wondered what thought he'd given to that profile and he said, "Oh, I think it sounds a little bit arrogant, but I might use the word gravitas."

I had a really foolish question, which I wasn't sure I'd ask. It depended on how things were going. I could pretend I asked it to test his tolerance, but unfortunately I really am shallow enough to want to know: What is it with scientists and beards?

Despite his gravitas and my shallowness, he didn't mind the beard question a bit. He said, "Well ... in 1972 I spent three months in the Himalayas [with Sir Ed Hillary] ... doing medical research and I didn't shave and I've never shaved since." But why does he like having a beard? "Because it's three minutes less getting organised in the morning. I don't think it's got anything to do with body image."

He is not much given to self-analysis. "I reflect on science and all my responsibilities, but I'm not a person who is into great self-reflection." He thinks this is a generational trait; that his generation is not as "self-indulgent". He says he hasn't much examined what ambition means to him, although, he says, "I was ambitious from the day I left primary school." To him, that's simply a fact.

So it was probably silly to ask whether he was a prima donna. His great mentor, Sir Graham Liggins, who died last month, had said he could be. The quote, about the time Gluckman spent in the paediatric department at the University of California, was that "only prima donnas have their place, Peter more than held his own".

He spluttered and said, "I didn't know he said that about me! Hmm. What shall I say?" He said something affectionately rude - "the bastard!" - about Sir Graham. He says, of that time, "1970s science in America was a very egotistical, aggressive place ... a sink-or-swim environment. I think the New Zealand can-do approach survived very well in that difficult environment."

I'll take that as partial agreement. He says he's "not often" temperamental. On what occasions might he be temperamental? "I guess I can get a little tetchy ... upset if people don't deliver ..." He might shout "once in a decade. I mean, no more than anyone else. I'm just a human being."

No he's not. He's a super scientist and I know this because I read it in the Herald. "Yeah, and you write for the Herald, so it can't be right! And you can quote that one!" Did I say blunt? He can also be effortlessly rude but he takes such childish joy in this that it's impossible to be offended.

I took some childish joy in telling him he is also supposed to be "the closest we have to a rock-star scientist", and I read that in the Herald too. I'll take a punt and assume that he thinks this is silly. "Of course it's bloody silly."

A serious question: How did he measure his achievements in his role as science adviser? He is a translator, of sorts. "Of course." He makes public statements about, for example, climate change. His specialist area is, in lay person's terms, how the start babies get in life affects their later health status. He said, when asked, "I don't know anything about climate." He regards his role as understanding the scientific process and helping the public understand it. He said, "Oh, I've changed the dialogue." He knows this because "even Granny Herald writes positive editorials about science and its role in economic and social development in New Zealand".

Now, really, that "Granny Herald" is far ruder than calling somebody a "rock-star scientist", isn't it? He was inordinately delighted with himself. "Well, it might be! You probe me so I'll probe you!"

He is intensely competitive, probably about almost everything, if that exchange is any indication. It has been written about him, more than once, that "he has accumulated positions, power and funding at the expense of a long line of former colleagues". This, you'd have thought, was fairly damning and I thought, if anything did, that would make him cross. But he said, mildly, that while he thought it unfair, "I think it is inevitable and I've seen it happen in science all the time when you have a scientist who's successful." He works in large teams, he says, "and naturally others who have their own egos want to split away and I don't mean that in a negative sense at all." Perhaps he was a tiny bit put out. He banged on the table and said, "I mean, I've been successful! There's no denying the success of the track record!"

When I asked if having a reputation for arrogance would bother him (the short answer is "yes"), he wheeled out the tall-poppy-syndrome theory. I interrupted by rolling my eyes. He said, "It's a horrible cliche, but one that does still exist. I don't think I'm arrogant at all." He paused for effect, possibly in a rock-star scientist-like way, and said, "I also don't believe that I'm a humble, modest, retiring individual!"

He said, "I am who I am. I am a scientist who has had a good scientific career, who has been willing to also engage in building scientific institutions and continues to do so and has clearly had recognition from his peers."

Except, I said, to get him back for his Granny jab, those peers he's trampled on his way up. "I didn't! I mean, that's New Zealand's mythology about success." But does this bother him, really? "Yes, of course it bothers me if people think I've been Machiavellian. Because I'm not. It just says that people are making a superficial assumption about what I do."

But, as he is not given to self-reflection, he wouldn't know what he is really like, would he? On reflection, I could probably have guessed that it would be just like him to get the last word.

He said, "Well, does anybody else know what I'm like? I do have to run."