Just nine days before his death, Sir Paul Callaghan gave his last interview. He talked to Nikki Macdonald about life, death and his vision for New Zealand.

Sir Paul warns that he's on morphine and sedatives so might tire or say strange things.

His family is listening in to protect his interests.

ANDREW GORRIE/Fairfax NZ MAN OF MANY PARTS: Sir Paul Callaghan was proud of New Zealand and New Zealand was proud of him.

Back home after almost a month in hospital, he knows death is not far away.

He'll talk for 10 or 15 minutes, he says. Any longer and he'll need a break.

But for 30 minutes he talks eloquently and lucidly.

That ever keen mind never falters.

And the only tears are reserved for those less fortunate cancer sufferers – the young, the mothers, who were robbed of their chance to live their lives to the full.

Yours has been an incredibly full life. The list of achievements and accolades is ridiculously long. What are you most proud of?

It's insane, exponential madness. Give a guy a prize and somebody says, "This guy's got a prize, he must be good, let's give him a prize."

Obviously I'm most proud of my family. I have two wonderful children and a couple of wonderful grandchildren, a wonderful wife. I've been very lucky. My family have supported me. It's my second marriage and my first wife did a lot to support me as well. That's on a personal level.

As a scientist, you get a lot of scientists complaining they're not paid enough, it's a terrible job. I can't understand these people. I've had a wonderful life as a scientist. I always say, if you want to make money go into business. If you want to follow your heart you've got to take some risks in life. If you think it's tough being a scientist, try being an opera singer or a rock star.

I have travelled to all sorts of places, have friends all over the world I've collaborated with, across every boundary of culture and nationality and outlook. It's been extraordinary really.

Professionally what I'm most proud of is the young people that have come out of my lab.

I've had 24 PhD students, numerous masters students and all the people I've taught at undergraduate. The graduate students have all done incredibly well. Everyone who comes out of my lab gets two or three job offers, all over the world.

There's a group of about eight or nine in New Zealand. Of those, five or six are behind this wonderful company Magritek.

Of all the things I look back on – I've done some world class science and been highly productive and been well recognised for that – but the company is something I'm deeply proud of. Because a lot of people talk about commercialisation. We did it.

In 2004/05 we started a company with two staff. We've got 23 now, we export $3 million a year and we're growing like hell.

Very soon we'll be about 30 staff. We are manufacturing some of the highest tech product around.

We sell magnetic resonance spectrometers to the international petroleum industry, the pharmaceutical industry, academia and research, the food industry. We've found a market niche and we've carved it out. Our products happen to be the best in the world. If they're not, we don't export. That's the name of the game.

We stuck to our knitting – we know what we're good at. I'd spent 35 years building up expertise and training up young people in this area. We're no good at making cellphones. We're no good at making respiratory humidifiers. We're bloody good at making magnetic resonance spectrometers.

We're not big. Let's not get carried away – we're just a small company. But we had sales from day one. Every year we've brought out new products. We've ploughed the profits back into the business.

You go up there in that company, there's just a buzz. These wonderful young people just loving what they're doing. Of the 23 staff I think we've only had two leave in seven years.

There are some geniuses in that company. I'm just one of the ones that started it. It's the sheer quality of the people. And you've got to strive for excellence. If you're not the best at what you're doing, don't bother.

Is there anything you would do differently?

I would have been a better person during my life, behaved better. Particularly when I was young. But we only get one chance, don't we. I was a naughty, exuberant, outspoken, troublesome teenager.

I got in my fair share of trouble, but I got away with things. The number of times a kindly local policeman said to me `Paul, you do that you're going to end up in real trouble. I'm letting you off this time but you go throwing stones on the roof of the public toilets in Hill St again ...' That was one of my crimes. I was probably caned more than most kids at school. And deserved it.

I grew up in a town where people gave you a break. Boys are lethal behind cars. I was a silly young man and there were a couple of times I was very lucky not to have hurt anyone. Traffic officers, as they were then, took me aside and gave me a break. Learn from that.

I often say it would have been wonderful to compose music for the film industry. I love cinema music. I was musical. I played in a brass band, learned the piano. I learned musical theory and I actually wrote a few little things when I was young. My daughter is a far better musician than I ever was.

In terms of the life I've lived in science, I don't have any regrets. There was one mammoth task that I wanted to complete and that was writing this huge book. I wrote a big book in 1991 about my field of research. It was a bestseller in its genre – you won't find it for sale at airports.

Since then a lot has gone on in my professional world so I wanted to write a new book. I started it the year I was diagnosed with cancer, in 2008. So I wrote most of that book while I was having chemotherapy, surgery.

I feel so proud and pleased that I got it done with time to spare and time to really make a nice job of it. It's lovely.

A month ago you chose to deliver a lecture on Zealandia, despite being so weak you feared you wouldn't last the talk's duration. What motivates you and how do you carry on through the pain?

What greater sense of fulfillment can there be but to make a difference to the community in which you live? It's one of the reasons I wanted to come back and make my life here, as I say to our diaspora, that's the real opportunity New Zealand offers. It's hard to make a difference living in New York. Here everything you contribute makes a visible difference.

And, with the cancer, I resolved that I would not waste a day, that every day I would fill with purpose and spirit.

Why Zealandia? Zealandia is one of the best organisations I have come across. And then there is the amazing conservation success story. Instead of cheap shot environmentalism parading about palm oil or arctic drilling, we are about actually doing stuff in our own backyard, remediating the tragic loss of our taonga. And for goodness' sake, this is something Wellington has led the country in. Aucklanders could only dream of such a native bird density in their gardens. Finally, funding. Yes, these are tough times, and that makes the "public good element" always hard to argue. But can we have a reality check? What we are asking for is small compared with the annual subsidy for the Zoo. I think Zealandia has the capacity to inspire the nation, as I laid out in my talk. But you are right. The talk exhausted me and I was hospitalised two days later. But hell, I would do it all again!

You could have worked anywhere in the world. Have you ever regretted returning to New Zealand?

No. And I've had many job offers from around the world, some of them quite bizarre, actually. Would I like to be vice-chancellor in Ireland? Obviously I've had fantastic research offers of running major labs in the United States, Australia. I never considered them for a second. Why? Because New Zealand is my home. My family's been here for 150 years. For me, it's the most interesting country in which to live.

I can be myself here. When I get up and say 'I'm not happy with the way the country is going', nobody can say 'Well, why don't you go back to where you came from'. I have a sense of ownership. My family has roots here. I have friendships here. I like the people of this country. You get on the phone to sort out an insurance problem or a car registration, it's a piece of cake. You do that overseas and it's a bloody nightmare. Everything's so easy in New Zealand. I know we've got our social worries. But for most of us New Zealand is a wonderful country in which to live.

What is your vision for the New Zealand of your grandchildren?

A place where they would see an opportunity to live the life they would best imagine for themselves. That would be something to aspire to as a nation, wouldn't it? It's about creativity. It's about anything that gives jobs, creates prosperity, enables us to do the things we want as a nation and doesn't focus on money for its sake but for creating a better society. It's not about pie in the sky. Yes, we have heard it before, but who's actually done it? That's the point. We need leaders that are going to do it. Stop talking about it and stop reshuffling chairs on the Titanic.

I'm totally optimistic we will get there. Because I've been talking to audiences all round this country. The reception I've been getting is the same everywhere - we want that long term vision. Any politician that has the guts to stand up and say 'Actually we're going to do it' I believe will have the will of New Zealanders. It's not about Left, it's not about Right, it's about getting stuff done. That's where the future is going to be. New Zealanders are not stupid, no matter how many cooking programmes they watch on television. They've got good instincts, I think.

I really think I've got a bit of traction with what I've been saying in the last couple of years. There's some stuff going on in our social political framework that I feel very happy to see being picked up on. We are blessed. We have ample water supplies, renewable energy in abundance, pristine natural environment, a good education system albeit with inequities. If we can get the mix right, where talented, creative people want to come and live here, not just because they've got bucketloads of money. It's about coherence - the way education connects with the innovation section, connects with business, connects with the environmental aspect.

Last year you were named New Zealander of the Year. How does it feel to have an entire nation look to you for wisdom?

It gave me a vehicle. That mantle was put on me and immediately the media wanted to hear what I had to say. Downside - people starting writing stuff about your personal life that impacts on you and your family. You become public property and you hear all sorts of freaky stuff and you just have to learn to deal with it.

Has there been a transformative person in your life?

There have been a few. Amongst New Zealanders I hold Blakey (Peter Blake) in high regard. Ray Avery is a lovely man. Richard Taylor of Weta. Dan Walls, a great NZ physicist, Harvard educated, who chose to come home and lead the world from here. He died of cancer in 1999.

I got into science communication because of Alan MacDiarmid. He did his lecture series around New Zealand, packed town halls. He just resonated with New Zealanders. He touched audiences. I realised people were interested in science but there was a framework in which you had to operate to make it interesting, to tell them stories, to give them a thought about where we're going in the future, what the possibilities for our country are. He was an inspiration to me. I admire people like Peter Gluckman and Shaun Hendy who have been wonderful leaders and carried this torch.

It's not that scientists know it all. Science does not teach us how to live as human beings, how to raise our kids. But it gives you a perspective on how to look at the world and so long as we stay true to our profession and don't go advocating things beyond our competence, but we just alert society and inform them about where things are going - medicine, global climate change - and how it's going to impact on their lives. These are all issues humans have to grapple with and apply their ethical values to. Scientists have no more ethics than anyone else but they do have some information. And they have something else - an understanding of what numbers mean and what they don't mean. They don't have quite the same fuzzy view of nature. We find nature profoundly beautiful and profoundly rational but absolutely not known.

That's one of the things you discover as a cancer sufferer, you come into contact with young people. I remember young Kurt Filiga, who made a film about his life. He and I would sit opposite at the day ward down at the hospital [sobs quietly]. You can't help be moved by the courage of people much younger than you, young mums with kids. I'm the guy who has had the most out of life anyone could ever have wanted. I never felt sorry for myself for a single moment. I call them the comrades, people like Winnie Laban, Fran Wilde. It has been a special bond between people who have been down that road. I've found that an enormous privilege in a way.

What will you most miss for the 20 years you're no longer here?

I could concentrate on what might have been, but what's the purpose of that? We all face death. I could be 85 years old, all my friends have died, I'm in an old folks' home. I'm fortunate in many ways to die a robust and healthy man. Those memories of myself are all that they know. There's a lot of upside.

You must have had a lot of time to reflect in recent months. What are two of your happiest memories?

Last year my wife Miang and I had a sabbatical in Cambridge. My son lives in Cambridge with two beautiful children and my daughter lives in London. We went together on a family holiday to the south of France. It was the most extraordinary time, in this little villa down there, eating wonderful food, swimming in the swimming pool, going for walks amongst the sunflowers and the French lanes.

The other happy moment was in 2009. My wife, who has spent a lot of time in the United States, knows the national parks there very well. She took me and we went for a tour of five national parks. We're not the only beautiful country on earth. I've climbed mountains in Slovenia, I've walked in the mountains between Poland and Slovakia. I've always been a great outdoors man.

You're an atheist. Has that made it easier or more difficult to come to terms with death?

I'm an atheist in the sense that I don't believe in an omnipotent, all-knowing, omnipresent creator.

That's not to say I'm not a spiritual man. I acknowledge the mystery. In the sense that there are questions there that are not answered by simple paradigms around evidence and consistency, which is the way science works. Around values and why we're here at all. The point is the singular chance that you should happen to be born. What is the chance of that? Zilch. But when we die we go back and we're not around any more.

So I feel there's nothing to fear from death. What can I fear? I've been under general anaesthetic, I know what it's like just to disappear. I have no fear, only regret I'm not here to share more of my life with my kids.

How do you hope that you will be remembered?

As having made a difference.