"I first became interested in antiques when I was a schoolboy," Mains said. "But it was when I was in London that I really caught the bug.
"I decided to return to Auckland to start up my own place and I never looked back."
In between, Mains enjoyed a spell as errand boy for the late, great TV and film actor Peter Sellers in London.
"Apparently I got the job because his secretary thought I looked a bit like him."
He was also a lift operator at the word-famous Selfridge's store in Oxford Street. And he even had a stint as an apprentice french polisher in Sydney.
"An old school friend of mine Matthew West was in London at the same time as me and he was working for Peter Sellers," Mains said. "I ended up being taken on as Peter's unofficial errand boy.
"But Matt had some very glamorous friends and he mingled with people like the Beatles and big movie stars like Judy Garland. It was all very exciting.
"Peter Sellers was great to us. He knew I didn't have much money and he used to come around to the flat Matt and I were sharing and would give us presents.
"I remember he once gave me a chest of tea and another time I was given a set of copper-bottom saucepans.
"Peter was nothing like his public image. He was a superstar but he was also very shy and kind."
When Mains returned to Auckland to open Portobello Antiques, he soon found people queuing outside his shop.
"Within two weeks I was cleaned out but I had wonderful support from some well-known Auckland families who would give me things to sell.
"New Zealand has a very rich seam of antiques because of all the old families who migrated here back in the day."
Mains admitted he has unwittingly bought one or two duds down the years while on buying trips to Europe but said a good profit can be made from dealing.
"It has been a fabulous journey and I won't stop now because I suspect I will still keep an eye on the auctions. But I have never done this just for the money. It has been a lifelong labour of love."
Cordy's owner Andrew Grigg said he expects the auction, held over two sessions on Tuesday, to be packed.
"John has been at the pinnacle of the antiques business in New Zealand for an awful long time, and his stuff is always beautifully presented. He is the man the rest of us have always looked up to."
