On Thursday, Hugh Green, 79, was outed. At a little ceremony at his company's offices in Onehunga, he presented Sir Ray Avery's charity, Medicine Mondiale, with $500,000 for the development of an affordable, quality incubator that will save the lives of babies in developing countries.

Giving money away is something of a habit that had gone beneath the public radar before publicity surrounding his latest donation.

Late last year, the Centre for Brain Research at Auckland University received $1 million (over five years) from the Hugh Green Charitable Trust. He's given $300,000 to the Malaghan Medical Research Institute's cancer cell research group and $1 million to set up a fund to support diabetes and breast cancer research.

St Vincent de Paul, various Auckland hospices, the restoration of St Patrick's Cathedral and the St Patrick's Day parade are other beneficiaries. "He just goes about it quietly. It's the way it's always been," says daughter Maryanne, chief executive of her father's company, the Hugh Green Group.

What has changed is the frequency. So much so that son John has had to scale back time spent at his racehorse-training partnership to vet and organise the charitable side of his father's activities.

Green recently sent $70,000 to Grey District mayor Tony Kokshoorn to help families of Pike River miners who died and is in the process of making a contribution to help the Christchurch earthquake recovery. "He sees these things and says, 'we need to give them something'," says John.

"Did you tell him about my girlfriend, Louise?" quips Green in his still-rich brogue to his son as the Herald is leaving. He's referring to Louise Belcher, manager of the Papakura family centre, part of Dame Lesley Max's Great Potentials charity, which teaches parenting skills.

"I feel good about supporting people when you see the time and effort they put in for nothing or for very little financial return," says Green.

GREEN LEFT school at 12 to become a drover, guiding cows to cattle marts where mental arithmetic and the ability to pick a buyer who would make good his promise to pay were essential survival skills.

As the son of a publican who was his own best customer, Green says the family was "on the bones of our bum".

The advent of the lorry dried up droving work and at age 19 Green sailed on a £10 assisted passage to Australia with a plan to make enough money to return to Ireland to buy one himself. After stints labouring on hydro schemes and cutting cane, Green fell in with some Irishmen digging trenches in Melbourne for 1s 6d a foot - good money at the time. They then priced and won a job digging trenches and laying water mains, which earned them as much as £100 a week.

In 1952, with £1200 saved and in the company of another native of Donegal, Barney McCahill (father of former All Black, Bernie), Green decided to travel home via New Zealand and Canada.

In Wellington, they won a tender to lay cables for the Post and Telegraph Department, followed by another to lay 21 miles of cable around Auckland City. The fledgling Green & McCahill (Contractors) Ltd bought a digger and expanded into tunnelling, sewage and stormwater contracts and grew to become a major operator in infrastructure projects throughout the country.

The company's success put both men on the rich list. Green's fortune - boosted since 1980 by the acquisition of farms on the fringes of Auckland, land development, oil and gas exploration and shrewd investment in the stock market - was recently said to be $190 million.

His land bank has him sitting pretty for the future too, able to cash in as Auckland spreads. But, he says, he didn't buy land because it might one day be carved into sections. "I bought if I thought it was value in itself. If you own land, it can only go up in value.

"People say I must have had great vision but I really had no vision. I was day-to-day. I tendered for jobs I thought I could do and worked very hard to get them up and going. It just all happened. You never said 'I want to have so much money in a certain amount of time'."

Ask about golden business rules and he tells you to keep a tight rein on costs and he's not into leverage. He never bought anything unless he could afford it.

Apart from business being a little quieter, the current world downturn hasn't affected his company. "We don't owe any money to anybody and that was the secret of our success.

"I see people starting out who have a few quid and they see an overdraft from the bank as the answer but that's no answer at all. The important thing in the construction business is to get your costs right or you're gone."

But there were scary times - tenders he and McCahill won that were out of their league but which they got done through perseverence, a close call building the Hamilton road by-pass during the 1974 oil shock when the cost of diesel soared from 14c a gallon to 76c during the project, another close call building the Te Marua water-storage twin-lakes in Upper Hutt.

In the Hamilton case they were saved by a contract clause that covered them for any increase in the cost of machinery hire - "but it took a lot of scrapping". They were down $5 million on Te Marua until they won all three arbitration disputes. The point being that by then they were big enough to fund fighting in court. It would have knocked a poorer company over, he says.

"You never thought of losing. You wouldn't rest, you'd keep at it."

He's pleased about plans to make resource consent processes more efficient and says New Zealand must make more of what is in the ground. Gold, coal.

"Ireland is pretty down there now but New Zealand could follow. We have a lot of debt. It's only the dairy industry that is keeping us up now."

Of the Government's goal of closing the wealth gap with Australia, Green says "we have as much chance of leaping over the moon" but we can make much more of what we have. We should be getting minerals out to strengthen our balance sheet. It might blot the landscape in a few places but what about it? It can be managed."

New Zealand and Irish flags fly out front of the Hugh Green Group offices in Onehunga. Green, who is battling prostate cancer, never did make it back to Ireland to live. Work, love and marriage (to Moira, they have five children, 11 grandchildren and one great-grandchild) got in the way but he makes annual trips and professes a great love of both countries.

Ireland recognised a great son when in 2006 its national university presented the school drop-out with an honorary doctorate of laws. Not one for honours, Green surprised himself with how much he enjoyed the experience. Honoured that day were a philosopher, a papal knight, a clinical pharmacologist, experts in post-modernism, algebra - and a former boy cattle drover.

Though a republican, he's pleased New Zealand has recognised the likes of Dame Lesley and Sir Ray and he's grateful he found here the opportunities that have given him the wealth to give back by helping the likes of them.

His simple litmus test can be seen in how he came to first met Avery a few years ago. "I read an article in the Herald and thought, 'here's a fella who is doing good work for no profit for himself'.

"That's the sort of people who you would like to help."