He may have been diminutive and unassuming, but "Uncle John" Bonner was no pushover.
After a decade developing radar for the RAF, the technology lecturer passed on his knowledge to pupils in some of the remotest parts of the world. From Papua New Guinea to East Lothian, he won pupils over with a combination of intellect, joviality and casual sarcasm.
John Bonner was born in West Hartlepool in January 1927, one of only two surviving children among five brothers and sisters.
After a year at secondary school, "Ginger Bonner" - the name referred to his auburn hair - sat the entrance exam for technical college and was apprenticed to a marine engineer. The course did not appeal, however, so he instead enrolled at Yorkshire's North-Eastern School of Wireless Telegraphy.
Here, he found his metier. He had an intensely mathematical way of viewing the world, and technology made immediate sense to him. Initially, he hoped to become a radio officer with the merchant navy, but a childhood incident of epilepsy meant he could not be sent to sea.
However, a new area of technology appealed: radar. He therefore signed up with the RAF for a mandatory 10-year service. Word of his technical adeptness quickly spread: whenever there was a problem no one else could fix, someone would send for Sergeant Bonner.
When, in 1948, the Western allies organised a drop of supplies into West Berlin - known as the Berlin Airlift - he was among the air-traffic controllers directing relief planes.
By 1951, he was back in Hartlepool. One Sunday evening, as he stood with friends outside a local church, he was spotted by Eunice, a young chorister. The two began spending time together, and he introduced her to Heinz baked beans, a forces staple. It was over a simmering pan of beans that John asked whether his serviceman's wages would cover the cost of housekeeping. They married in October 1952.
He was a quiet, intensely modest man. "I speak when I've got something worth listening to," he said. Though he was offered commission in the RAF, he preferred to remain one of the boys. He found immense satisfaction training others in radar science.
And so, on his discharge he qualified as a technical teacher. Shortly afterwards, he found his dream job as civilian education officer at the RAF's Number 1 Radio School in Somerset.
Jovial and likable, he was immediately at home in the classroom. "Listen to your Uncle John," he would tell pupils, and the nickname followed him throughout his career. At 5 feet, 4? inches (the quarter was important to him), he relied on good-natured put-downs to keep pupils in place. "Uncle John doesn't run evening classes," he said when boys turned up late to lessons, and "I'll thump you" when they did not listen.
But he cared, and his pupils knew it. Despite his pronouncement on evening classes, he would offer after-school coaching to any boy who asked. And, on Saturday evenings, a dozen pupils regularly materialised at the Bonner family home, looking for food and drink.
Following cutbacks at the RAF school, Mr Bonner was made redundant. In 1969, therefore, he joined Leith Nautical College as senior lecturer. Here, he indulged his frustrated naval ambitions, organising school sea-fishing trips. He also bought a boat, and took his two children, Andrew and Joy, on trips around the Firth of Forth.
Technology dominated home life, too, often literally: the Bonner living room was filled with hi-fi speakers the size of kitchen cabinets. And, from the 1970s onwards, he made a point of owning the latest computers.
In 1975 the family moved to Fiji for two years, where Mr Bonner taught electronics at the island's technical college. Relocating was not a difficult decision: he had an innate wanderlust, and would see a job advert, think "why not?" and apply.
It was the same reasoning that led to a move to Saudi Arabia a few years later and, in 1985, a two-year posting as senior examinations officer for Papua New Guinea posts and telecoms. His travels were not something he boasted about: he just quietly made the most of life.
After part-time work at a college in the Lake District, Mr Bonner retired in the late 1980s. Ten years ago, he and Eunice moved to the Orkney Islands to be near Andrew. Here, he would watch in amazement as his granddaughters demonstrated the versatility of their mobile phones.
John Bonner died on 17 June. "God must have a job that no one else can do," a friend commented.