James Herriot wrote about his first canine passenger in his fourth book, Vet in Harness, referring to him as a beagle named Sam.

Having him with me added so much to the intermissions I granted myself on my daily rounds. Whereas in offices and factories they had tea breaks, I just stopped the car and stepped out into the splendour which was always at hand and walked for a spell down hidden lanes, through woods, or as today, along one of the grassy tracks which ran over the high tops.

This thing which I had always done had a new meaning now. Anybody who has ever walked a dog knows the abiding satisfaction which comes from giving pleasure to a beloved animal and the sight of the little form trotting ahead of me lent a depth which had been missing before.

Sam the beagle is an example of James Herriot’s habit of making a composite character out of one or two others. Sam is, in fact, Danny and Dinah rolled into one.

Such was his feeling for the canine race, Alf never understood how anyone could live without a dog, let alone walk without one. One day, he and I were exercising Dinah along the side of the Codbeck, a popular route with the dog walkers of Thirsk. A man whom neither of us recognised strode by, whereupon my father said to me, ‘That’s a suspicious-looking character! I wonder what he’s up to?’

‘Why do you say that?’ I asked. The man looked fairly normal to me. ‘What’s suspicious about him?’

He gave the retreating figure another glance and smiled. ‘He hasn’t got a dog!’

All good things come to an end, and in the spring of 1954, Alf was very sorry to learn that John Crooks was leaving to establish his own practice in another part of Yorkshire. He would see John depart, to be replaced by another young veterinary surgeon – a pattern that would be repeated many times across the portals of 23 Kirkgate.

James Herriot talks about only three veterinary assistants in his books – John Crooks (to whom he gave his real name), Calum Buchanan (real name, Brian Nettleton) and Carmody (who is described as a student in the third book, Let Sleeping Vets Liebut who, in fact, was an assistant named Oliver Murphy). There were, of course, many others. Over a period of forty-eight years to the present day, upwards of thirty young people have worked as assistants in the practice – all providing a rich variety of personalities.

James Herriot writes about his sadness at the departure of John Crooks and how this was tempered by the arrival of the unforgettable Calum, complete with his badgers and an assorted menagerie. Brian Nettleton, the real Calum, did not actually arrive until 1957 and there were, in fact, four other assistants in Thirsk in the meantime – men whom Alf never mentioned in his books.

The assistant who followed John was a young man called Jim Chadwick. Had my father ever written another book, he may well have figured in it. While researching my father’s life, I came across some work he had put on disk for future reference, among which there is a great deal of material about Jim.

Jim Chadwick was a handsome young man who soon became a great favourite with the ladies. He was not only handsome but charming, and turned out to be a real asset to the practice. He was a very good veterinary surgeon but in his first few weeks lacked confidence, continually appealing to Alf to extricate him from sticky situations. He told me, years later, how grateful he was for all the valuable support he received during those first uncertain weeks.

Alf did not mind; he preferred to have a young man who was willing to listen and learn. I remember another assistant who adopted a different attitude. Believing he knew everything, he refused to heed advice from his more experienced employers. The result was some disastrous mistakes on the farms which gave Alf and Donald many sleepless nights.

My father’s old friend Eddie Straiton, for whom I worked for fifteen months, had little time for newly-qualified assistants who thought they knew it all. He had a forthright way of expressing his views. I’ll tell you what’s wrong with such people,’ he said to me one day. ‘They don’t know enough to know they know bugger all!’

Jim Chadwick, however, had the sense to know that he had a great deal to learn. I asked him to tell me about his time in practice at Thirsk.

‘I learned more in six months with Alf Wight and Donald Sinclair than I did in five years at university. The practice of Sinclair and Wight was a model which, in later life, I have always sought to achieve. I have had two people that I have tried to emulate. One is J. G. Wright, Dean of the Faculty of Liverpool Veterinary School, the other is Alf Wight.’

Jim wrote about one incident which smacks of life in Skeldale House with the incomparable Siegfried.

‘I never saw Alf Wight put out but Donald Sinclair had his moods. I can remember the dressing down I received when I dropped a glass syringe which, of course, broke. Imagine my delight when a few days later Mr Sinclair did the same thing. I did not think it politic to comment though I did see the twinkle in Alf’s eye.’

With the TB Testing work increasing, the work load became such that another assistant was appointed – Ken Hibbitt from Bristol, who had seen practice with Alf and Donald as a student. He arrived in November 1954 and he and Jim Chadwick became great friends. His arrival meant that Alf could now dispense with night work completely – an almost incomprehensible luxury. The early 1950s were some of the happiest days of his life. As well as having the pleasure of spending time with his family, he was working with men he liked, while doing a job he found fascinating and rewarding.

Ken also wrote to me about his time working in Thirsk.

‘Alf was a great person to see practice with and he was equally good with the new graduate starting a professional career. He did not restrict his young colleagues solely to TB Testing and dehorning and other routine jobs but gave them an opportunity to visit the more interesting cases without interference. On the other hand, he was always available for discussion and pleased to offer advice. If an animal died, he was sympathetic and attempted to boost the confidence of his disappointed colleague. I well remember losing a cow suffering with fat necrosis within the first few months in Thirsk and being reassured by Alf that I could have done no more. He pointed out that he could use a small field to bury all his failures.’

Although the two young men relished their time in Thirsk, they had to work very hard. They received only one weekend off in five, with out-of-hours work extremely common. When on call, they would be almost certain to be on the road.

Alf knew that Ken would not remain in Thirsk. He had the brain of an academic with an ambition to take up a post in teaching and research. He left in February 1956 for Bristol University, where he lectured in Biochemistry, and attained a Doctorate of Philosophy in metabolic disease.

Ken’s departure meant that another assistant had to be found and, in that same month, Oliver Murphy arrived. I am sure that, should his name be mentioned to the older clients of our practice, they would not remember him at all, yet he is one of the few assistants upon whom James Herriot bases a story.

Oliver, a serious-minded young man who was also bound for an academic future, stayed only four months in the practice. Although having little idea of how to handle farm stock, and becoming involved in some frightful rodeos, he was a pleasant young man and the farmers liked him. They liked him because he was a trier; he never gave up. Alf used this to effect in his books, describing Oliver as ‘Carmody’ the student – the young man who stubbornly hung on to a rope attached to a rampant beast while being towed through oceans of manure.