Patel doesn't want me to mention the price because he thinks it will give his competitors an advantage.
It seems strange to me, since any of them could ring him up and ask him for a quote at any time, but I'm happy to oblige. Anyway, if the truth be told, Patel's not much bothered by competition these days.
He's slowing down, he tells me. Working when it suits him, "when I get the good one".
I've squeezed past the empty cardboard boxes occupying half the corridor and clambered up the stairs to his HQ just off the main street in the Sandringham Rd shops.
Patel's installed behind his cluttered desk, which looks much as it probably always has: a phone, stationery, pens. A computer is conspicuous by its absence.
"I like to see things in writing, properly," he tells me, by which he means on paper. It's hardly surprising, since paper has been the medium by which he's transacted business for almost half a century.
"I'm 68 now," he says, "and things are all going on the computers and all this sort of thing. Business is not that big now. Customers do want the service but the money's not there."
Under various names, but latterly as Circular A1 Distribution NZ Ltd, Patel was, until 1997, the second-largest distributor in the country after NZ Post.
"We used to have big contracts, including the supermarket chains, so we were doing all right."
Those big contracts have gone to competitors now - thanks, says Patel, to "a very silly man" at one of the grocery giants.
At the same time, modern marketing techniques, using new technology and social media, have eroded the letterbox drop as a way of drumming up business or communicating with customers.
It will still work for big businesses such as the supermarkets and The Warehouse "because people do have the habit of looking at what's the special today, you know?"
Born in the Indian state of Gujarat, Patel first settled here in the early 1960s and started delivering things pretty much right away: he put the Auckland Star in subscribers' letterboxes in the afternoon and then sold it on Customs St to city office workers heading home.
The progression into circular distribution was inevitable.
His eyes roll in mock horror when I ask him how many supermarket specials flyers and chain-store pamphlets his army of contractors - as many as 6000 on some jobs - have pushed into letterboxes.
"Billions," he says, beaming. "To do the whole of New Zealand today is 1.3 million households. We don't do that now but we used to do it every week."
He's aware that there are plenty who won't admire that achievement and he has no argument with them. He doesn't even resent it when people call what he delivers "junk mail".
"But," he adds, "those are the same people who will always complain that things are too dear. But they don't want to take something that is right under their nose and browse through it [so they can save money]."
And, recalling the days when promotions included free samples, he says "they'd be the number one who get on the darn phone and complain that they never got one".
