Emeritus Professor Stone, now 89, remembers that day in 1964 very well. "I looked at the first few papers and realised I had discovered the motherlode," he says.
Campbell was an inveterate recorder of everything he did. "There was never so comprehensive a record of the personal life of a businessman nor of a person who was widely acquainted with everyone of significance in Auckland at that time."
It took the librarians 13 years to complete the inventory. It took Professor Stone nearly 10 years to write the first of his books based on Campbell's journals, letters, notes, receipts and the rest.
The professor's specialty was economic history, not a popular field then, or since. "The holy trinity of research in history at that time was class, gender and race," he says. "I had cut my teeth with a masters thesis on a history of trade unionism but found I was doing a history of business, which was highly unfashionable.
"I realised if I was to work on the history of Auckland I had to know its commerce. The business of Auckland was business, I learned that very early."
It meant he had the city's history largely to himself and he remains the pre-eminent living authority on Auckland's past.
It is not easy, he admits, to interest Auckland in its past and he has a theory about that.
"Many who live here are, in a sense, outsiders, recent immigrants or the children of immigrants who retain cultural roots and loyalties embedded elsewhere. Naturally enough, they have as yet little sense of our heritage.
"But we mustn't assume they are uninterested in it or unable to benefit from knowing more about Auckland's past."
In his illustrated talk last night, inaugurating a Sir John Logan Campbell Lecture that the council intends to be an annual event, he aimed to present an image of Campbell younger than the patriarchal figure the city has memorialised.
"It's always troubles me that so iconic a figure should be perpetually locked in people's minds as the elderly gentleman we see in his portrait hanging in the Town Hall or embodied in his stature that we pass when we enter Cornwall Park," he said.
The reason for this, he suspects, is that Campbell was adopted as Auckland's founding father quite late in his life, in 1892 when the town was marking a 50th anniversary.
Auckland, he points out, had not celebrated first settlers like the Wakefield brothers of Wellington, the first four ships of Christchurch's Anglican gentry or the Scottish Free Kirk settlers of Dunedin.
"Even Puhoi and Katikati had founding fathers. But Auckland's first settlers were not meritorious people who were coming to establish the seeds of English society or anything like that. They were humble, distressed handloom weavers."
The real founder of Auckland was Governor William Hobson who transferred his tiny colonial administration from the Bay of Islands to the Waitemata a few months after the Treaty of Waitangi. But Hobson died within two years and the Government had long ago moved to Wellington.
Auckland's early merchants, meanwhile, had made a lot of money but they had mostly taken it back to Britain.
Campbell was no exception. Around 1855 he and his first business partner, William Brown, had made their fortunes and left their Auckland firm under management to travel and live at leisure in Europe.
Brown, like many, never returned to the rough colonial life. But Campbell came back in 1870, deciding Auckland was where he wanted to be. He established his farm on One Tree Hill, planting trees, vineyards and olive groves. By the time the city came to mark the 50th jubilee of the arrival of the immigrant ships Jane Gifford and Duchess Of Argyle, Campbell was 74, "widely regarded as the great survivor," says Professor Stone, "All the other early people had made a fortune and returned to Britain, or died. Most had died."
Campbell remained active in business in his 80s and became mayor of Auckland in 1901. By the time of his death in 1912, aged 94, he had given Cornwall Park to the city and set up the trust in his name that still administers it.
He had also published his own memoirs of early Auckland. The delightful book, Poenamo, has had several reprints since the first edition in 1881 and this year the Campbell trust engaged Professor Stone to compile a centenary edition that has been published as a beautifully bound volume containing a full facsimile of Campbell's original.
It is not easy to get the professor off his lifetime study to talk about his own life. His memories of Auckland go back to the 1920s.
His prevailing recollection of the city of his childhood is of quietness. "There were very few cars or machinery of any kind. From inside the house you could hear children playing in the street, and the policeman's whistle.
"I remember that, and horses. Life then was still shared with horses.
"We walked much more. You could walk right across Auckland in a couple of hours and people did."
Some of the council's 200-odd heritage events organised for the next two weeks will recall that time as well as the era of John Logan Campbell and his contemporaries.
"What better way to learn of our heritage," says Professor Stone, "than from the life story of one who came as a 22-year-old doctor from Edinburgh, a city overrun with doctors? Campbell saw Auckland as a settlement of the second chance."
What better way to hear about it than from the one historian who has made the city his dedicated study for so long?
More information
Auckland Heritage Festival runs until October 14. Events include displays, performances, tours, talks and festivals. The programme is online at http://tiny.cc/68zblw
