To Jack Byard, what he had produced was a guide to help visitors to the countryside identify the various types of sheep they came across on their travels.

To some people in the wider world, though, it turned him into what one website describes as an “expert in biodiversity” – a writer who is able to put into simple terms how animals and man co-exist.

The former mechanic, jewellery craftsman and school technician now finds himself, at the age of 72 and five years since his official retirement, deeply committed to a new fulltime career which attracts correspondence from India, Denmark, the Netherlands, Italy and Ireland to his Haworth Road bungalow home. And it’s partly down to the Prince of Wales.

Jack had the idea of producing a book about sheep breeds after discovering that most of the children at the school where he worked thought there were only two sorts – white ones and black ones. He knew from childhood walks with his mill-worker father that there were dozens. He told the children so, and they were impressed.

So he began his researches, contacting the various societies connected with different breeds of sheep, talking to farmers, acquiring photographs. And then with the help of his computer he assembled them into book form.

“My idea was that it had to be small,” he says. “People don’t want to be lugging big books around the countryside along with their walks guides.” So after consulting with his ten-year-old grand-daughter, Rebecca, who often went on country walks with him, he embarked on a trial-and-error exercise which finished up with a book the size of a postcard containing colour photographs of more than 40 sheep, each accompanied by about 200-words of description. And then he sent it off in search of a publisher.

“I got a number of rejections, like anyone starting to write does,” says Jack. Then he had one of those strokes of luck that can kickstart a project. He was contacted from Cumbria by a woman who had seen one of his prototype books.

Jack fills in the background: “She had come across four orphaned lambs at auction, and was told that if they didn’t sell they would be slaughtered. So she bought them, took them home and bottle-fed them. Her interest grew and now she’s an expert breeder of Ryeland sheep, supplying to the Prince of Wales, among others. She’d become friends with him and his secretary during the foot-and-mouth crisis.”

She asked Jack if he’d sent a copy of his book to Prince Charles, and urged him do so. So he posted a sample copy off. A reply came back fairly quickly. His Royal Highness didn’t know a suitable publisher, but he did know someone who might.

Jack took the royally-recommended course of action and contacted the editor of the Agricultural Registry Publishers, who in turn suggested he might get in touch with a small publishing firm in Ipswich called Old Pond.

He posted off a copy of his sheep book and was telephoned the following morning.

“They said they’d publish it even though it was totally different to anything they’d done previously,” he says.

They set to work improving on his design. “They’ve turned what was a frog into a prince,” says Jack modestly. It is, in effect, a polished and embellished version of his own rather impressive efforts.

It quickly found a niche market. When Jack embarked on the project he thought he’d do well to sell 500 copies. Know Your Sheep, priced £4.99, has just gone to its fourth reprint and sales so far have reached around 8,000. And now it’s been followed by Know Your Cattle (same price), which features 44 of the breeds you might come across in Britain which with the same format seems assured of a similar welcome from the reading and countryside-loving public.

“I’m an overnight success after 72 years,” smiles Jack, in the dormer room he uses as an office. With his one-man production line operating eight hours a day, he’s currently researching for books on horses, pigs and poultry.

“If the research is slow with one of them, I’ll concentrate on another for a while,” he says. “I don’t like sitting idle.” Next book due from the publishers, though, is another on sheep, logging some of the more unusual breeds such the Ronaldsay, which is found in the Orkneys and lives on seaweed.

And there’s also the possibility of a book on Alpaca, not to mention one on tractors – which continues the farming theme but with its focus on mechanical beasts is a major departure from concentrating on farm animals.

“I always wanted to be an engineer, or to be an opera singer,” says Jack, who is full of surprises. In fact, he trained as a singer for several years and had an audition with George Mitchell (of Black and White Minstrel fame). However, a serious accident in his early twenties put paid to that dream.

Half a century later he seems to have hit the right note with his new career as a writer and self-taught expert on farm animals.

If you want to know the difference between a Friesian cow and a Holstein (not easy, as they’re both black-and-white), where you can find a Luing or which breed is the descendent of cattle to be seen on cave paintings created in France 20,000 years ago, it’s all there in Know Your Cattle.

Jack’s just the man to ask if you want to know which breed is best to avoid if you come across a herd of them grazing across your right of way.

“Be careful with any of them, especially at the time of year when they have calves with them,” he cautions. And he adds, for the benefit of those who think they’re in no danger if there isn’t a bull in the field: “Remember, there are more people killed by cows than by bulls.”