"We go back about 20 years," Mr Buck said.
He had been in Belfast and had gone to Mr Rankin's Michelin star restaurant, and to his delight noticed that Te Mata Coleraine was on the wine list.
It was a rarity at that time for a New Zealand wine to make an appearance on a fine wine list on the other side of the world.
"So he and I have known each other ever since that encounter," Mr Buck said.
During a break in the filming Mr Rankin said he had worked in the Napa Valley and was open to a wide style of world wines outside the widely spread European varieties and he put Coleraine on his menu for one very good reason.
"It was just drop-dead gorgeous."
So of course a bottle of Coleraine had to be brought out for the meal yesterday evening.
That meeting two decades ago, and the global reputation Coleraine has racked up, led to the Ulster TV producers of the series getting in touch with Toby Buck at Te Mata Estate early last month and put the plan of a visit to him and the family winery, which they happily took up.
Te Mata Estate, and Hawke's Bay as a whole, is part of the eight-episode New Zealand tour being staged by Nick and Paul's Big Food Trip and the chefs were absolutely loving it and were brimming with praise for the locally sourced ingredients they use along the way.
"The produce here is superb — you can tell how fertile the land is — this is an absolutely beautiful place," Mr Rankin said.
His cooking colleague agreed.
"The last time I was out here was in 1977 so things have changed a bit," Mr Nairn said with a smile.
"The food scene ... back then there wasn't one and all the cars seemed to be old British bangers."
But he said the one thing that had struck him 40 years ago that had not changed was "the stunning scenery and the great weather".
The pair have been mates for about 30 years and while the show has a cooking core it is also about pursuing the links created by the Ulster Scots who went off to settle in all parts of the new world ... which includes New Zealand.
And they look at the regions and look at the histories and, as Mr Nairn said, "we collaborate and come up with a menu that's appropriate".
They were keen to ensure the "secret" dish for last night's special dining occasion for the Buck family would remain a secret so Mr Buck had to leave the kitchen when it was being put together.
One of the three courses was a fine chicken dish accompanied by potato gnocchi and leaf cabbage kale with herbs and flavoursome sauces.
The produce, the wines and the scenic images shot and produced by the nine-strong crew will eventually be seen by millions.
"This show is going to take Hawke's Bay to tables all around the world and that's great," Mr Buck said.
His grandfather had come from Coleraine and eventually came to New Zealand, so the link was forged for the naming of the very special wine.
Mr Buck wrote to the Coleraine council in 1983 and was given their permission to use the name for Te Mata's finest.
"And we've got a councillor from there calling to see us at the end of the month."
The link has never been stronger.
