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A Scot by birth, he was brought up on a pig and poultry farm in the UK. Uninterested in poultry, he specialised in pigs at Usk Agricultural College.
After working in the UK pig industry, he was eager to see the world and set off on an adventure with a tent on his back, wandering across Europe and then to Australia and New Zealand.
Mr Jackson met Kiwi wife Linda 21 years ago this month. She had never lived on a farm and did not know anything about pigs.
Their pigs are all kept outside, as free range as possible, at the foot of the Hunter Hills.
"In a way, it was probably my fault," Mrs McCallum-Jackson said.
"Once I learned the difference between caged and outdoor pig farming ... I always say to people, the only thing I knew about pigs was that of a pork chop from the supermarket. Now you would not catch me eating one unless it was ours."
Nearly 50% of their business was lost overnight as a result of the Covid-19 situation.
Set up to supply local restaurants and hotels from paddock to plate, their margin took "an absolute pounding".
"We had to look at everything we were spending. Staff have been absolutely amazing with all hands to the pump, doing everything they could. We had a huge loss in the first month but have picked up again," she said.
"While there is no profit, it has made us look at our accounting, which is not too bad a thing."
Online orders and sales at selected supermarkets meant they sold everything they had on the farm.
"It is back to business as usual really. Pigs have to be fed every day and staff have to be looked after — we just had to keep on going."
Mr Jackson attributed their success to a love of pigs
"They are intelligent animals that come with a challenge. They are fascinating — they can make you laugh and certainly amuse you."
Their pigs were processed by local butchers before it became too much, leading to the establishment of a small processing facility in Waimate.
Deciding in 2014 they needed a base with stronger transport links, they set up a processing facility in Dunedin and have remained there ever since.
"There are times you wonder why you are doing it — there are times you just have to work through your puzzles. You need to put your head down and get on with it."
The name Havoc Pork comes from first-hand experience.
"Pigs always have their own agenda — you never know what is going to happen next. They go a bit haywire with electric fences and so we called ourselves Havoc," he said with a laugh.
Mr Jackson takes their pigs to be turned into pork and bacon in their own specially designed truck, known as the “Havoc Hog Hauler”. This is to avoid the risk of disease from stock trucks on the farm, and minimise the shock to the pigs.