A tribute to the life and times of our cartoonist Harry Horse, who died last week.

HORSE, of course, was not his real name. It was, however, one he was happy to saddle himself with. I had always assumed he'd borrowed it from Damon Runyon's raucous Broadway stories, peopled with dudes and doxies, bootleggers, sharp cookies, hoaxers, dreamers and do-nothings, of whom Harry the Horse was one of the most colourful. Not for the first time, though, he confounded us. He had acquired the surname Horse, we learned, because when he was a kid a teacher misread his father's handwriting on the school register.

Thus prosaic Richard Horne metamorphosed into flamboyant Harry Horse. Where the Harry came from is anybody's guess. Damon Runyon is my best bet. What I am pretty sure of, though, is that Harry Horse truly came into being when, at the age of 17, he abandoned his native Warwickshire. He liked to tell how he tossed a coin to help him decide between Edinburgh and London. The former won. The date was engraved on his memory: December 27, 1977. "I'm glad it was Edinburgh," he recalled many years later in an interview with this paper, "because it was smaller. I would have been terrified in London, completely naive."

Naive is one word you could use to describe him. Throughout all the years I knew him he retained his sense of open-eyed wonder, of bewilderment, outrage, amazement, innocence. Things never ceased to amaze him, whether they were the machinations of unspeakable politicians or number-crunching publishers or unperceptive reviewers. He railed like an Old Testament preacher, his anger a joy to behold. And he looked the part too, dressed in long black trenchcoat, Napoleonic hat - his great-great-great-grandfather's, he said - big biker-style boots, a character out of Tombstone. For a while, he wore a Dali-esque moustache which, bizarrely, seemed to complete the ensemble. He was a tall, broad-chested man with dark, generous, gentle eyes, a mad laugh and hair which looked as if it had been out in a storm. There was always something very Heathcliffian about Harry.

My first contact with him - in 1983 - was a phone call. At the time I had a part-time job with Macdonald Publishers who had lately published The Ogopogo: My Journey With The Loch Ness Monster, the first book Harry had written and drawn himself. On the phone he was incandescent with rage. He'd just received a royalty statement, which can have the same effect on authors as income tax demands on the rest of the population. Sales of The Ogopogo were poor, almost non-existent in fact, and Harry was not pleased. He ranted, raved and threatened to set his father - a lawyer, he said - on us. I did my best to placate him but succeeded only in inflaming matters further. Not long afterwards The Ogopogo became the first children's book to win the Scottish Arts Council Award. Harry was 23.

Several years passed before our paths crossed again. It was 1990 and I was now working for Scotland on Sunday, then in its infancy and teetering on the edge of infant mortality. Its recently appointed editor was Andrew Jaspan, who later edited The Scotsman and The Observer before becoming the founding editor of this newspaper; he now edits The Age in Melbourne. Harry, recalls Jaspan, first came to see him in 1990, accompanied by his wife Mandy and his dog Roo, whom security guards insisted should be ejected on account of probable fleas. "One out, all out," said Harry. They all stayed.

At that time Harry was the lead singer in a band called Swamptrash, which he felt was not given sufficient recognition by the paper. Mandy, resplendent in micro mini-skirt and Doc Martens, was their No 1 fan. After getting that off his chest, Harry produced sketch books full of his drawings and in due course was appointed Scotland on Sunday's political cartoonist, delighting in lampooning the likes of Margaret Thatcher, Malcolm Rifkind and John Major. "I still have a cartoon of Major posed as a ridiculous Imperial Leader," says Jaspan. Graeme Murdoch, then Scotland on Sunday's designer, adds: "Harry is described as a cartoonist but he was one of our finest political artists of the last 18 years. In many ways he was from another era. His style belonged to the early 1800s of James Gillray and George Cruikshank, who developed the form we know today as the political cartoon.

"Harry was at his best fiercely penetrating the veneer of politicians and public figures and he could anger a lot of people but at the same time influence our thinking."

One of his defining drawings, recalls Jaspan, was commissioned to accompany a series, written by George Rosie, planned to counter the view of the English political establishment that Scotland was a subsidy junkie, living off England's wealth. "We set out to prove that the opposite was the case, if properly researched." Harry drew the accompanying cartoon which depicted English pigs feasting at Scotland's trough. I have the original and it resonates still, reminding me of those formative days in journalism and of the presence and impact of Harry. As Graeme Murdoch acknowledges, he could be "difficult and truculent" but that is merely an expression of the seriousness and passion which he poured into his work. With Harry, you could never predict when the next volcano might erupt. Hard as it is now to believe, his connection with Scotland on Sunday was severed over one of Kurt Cobain's guitar strings, which had to be cut to fit the space left on a page for a drawing of the doomed singer-songwriter. As cartoonist friend Martin Rawson says, Harry was "intoxicated" by the smell of burning boats and bridges. When his mind was made up no mule was more stubborn.

However, by now - the early 1990s - Harry's career had taken off in several directions. Swamptrash, though relatively short-lived, was highly influential. Among its members, Harry recalled in a blog written just a month ago, was a young drummer named James McIntosh who was self-taught on biscuit tins and tupperware. They busked outside the National Gallery and grew from a trio to a quintet, posing as a cajun band from the Deep South. It was not, Harry said, a serious concern. "There was no practice room. We learnt songs during gigs. We messed up endings. It didn't matter. The less seriously we took it, the more it took off." Harry - the frontman and banjo player - was called Billy Joe. "The music we play ain't country," he would announce to bemused audiences in pubs such as the World's End and Nicky Tams. "Hell no, sir. It's bluegrass ... all the way from Swampland ..." It was while touring in Shetland that Harry met Mandy, wooing her with his Byronic good looks, faux Confederate accent, bohemian joie de vivre and anarchic sense of humour.

Meanwhile, he was increasingly in demand as a children's author and illustrator. His first employer was Stephanie Wolfe-Murray of Edinburgh publisher Canongate, who in 1981 published Magus The Lollipop Man by Michael Mullen, the first book Harry ever illustrated. "He claimed it was his name and his hat that grabbed my attention," says Wolfe-Murray, "but no, I was won over by his talent and charm."

Though over subsequent years Harry moved on to other publishers, he continued to work on projects for Canongate. "One day he came into the office, rubbing his hands with glee," recalls Wolfe-Murray. "He had sold a long lost diary' to an antique dealer for a lot of money, probably about £25, I really can't remember. He claimed that he had stolen it from his parents' library and every now and again he would be prepared to take another. And he did, or so the hapless antique dealer believed. This went on for several weeks. Harry sweated over the creation of these diaries, soaking the pages in tea and heating them in the oven to give them an ancient appearance. They were works of art, filled with tiny delicate writing and wonderful little pencil drawings. Unfortunately one of my colleagues at Canongate spilled the beans to the antique dealer which put a stop to it. Now they will be collectors' items. The diarist's name was an anagram of Harry's real name, Richard Horne."

Such japes aside, and despite the inimitability of his newspaper work, I believe that Harry will best be remembered for his children's books and, in particular, those featuring Roo, "a dog of unknown breed and age", who Mandy and he rescued from Portobello Cat and Dog Home in 1990. Roo was a legend, hymned by poets, memorialised in six enchanting books, starting with The Last Polar Bears, and upstaging the late Sir Nigel Hawthorne in an animated film of that classic story. Visitors to Harry and Mandy's various houses - usually ramshackle and off the beaten track - remember an atmosphere more akin to The Darling Buds Of May than Cold Comfort Farm. Chickens strolled in and out, no clocks ticked and front doors were never locked. Roo - named after Mandy's grandmother, Ruby - was omnipresent, a constant companion, grateful (but by no means pathetically so) for fate having delivered her into such solicitous hands.

ONCE, playing pitch and putt, I managed to strike her twice - a soft thwack - with a golf ball. I don't think Harry ever quite forgave me. When she died last May, Harry emailed his many friends to relay the sad news: "Just a line to let you know that Roo has passed away from this life to the next. She did not suffer, but died in my arms on her favourite place, the beach at Meal in Burra. Feisty and determined to the end, Roo died like she lived, with her adopted family around her. We played her favourite songs while she lay stately in her basket and when it was time we took her for her last walk. She did not suffer and she left us stronger and ready to face the coming years with courage. She is buried at Kullade and a simple headstone marks the place."

As I type these words I can barely see the screen for tears. There will be those who find such sentiment silly. I doubt very much, however, that any of the recipients of Harry's email did. For they, I suspect, like me read in it the pain which Harry and Mandy were enduring, Roo's passing marking the end of a stage in their own lives which was irrecoverable, the sweet memory of a time when everything was possible, hope sprang eternal and nothing could beat dancing like a banshee to the sound of Swamptrash. By now, Mandy herself was gravely ill from multiple sclerosis and was confined to a wheelchair. In recent days, I gather, she had been failing fast. She was not yet 40. "I spend most of my days in the kitchen rather than the studio," Harry wrote. "I have a considerable number of teabags at my disposal."

He was often in despair. "I get the black dog," he once told my colleague Vicky Allan. "If I don't draw, then I get depressed. So it is therapy." Much in the world filled him with horror: war, global warming, rampant consumerism, random cruelty, inconsideration of animals, political lip service to culture, unappreciativeness of artists. His cartoons - each a work of art - got increasingly dark. An attempt to sell the manuscript of The Last Polar Bears to the National Library came to nought. He was offered pitiful sums for hundreds of thousands of copies of his books. Apparently, The Last Polar Bears sold over a million copies. If that's the case, it only goes to show how poorly recompensed are those who so enhance the rest of our lives.

As we await the truth about the deaths of Harry and Mandy, the supposition is that Harry assisted Mandy's suicide then killed himself. At this moment all that seems immaterial but one can't help but think that would not have been Mandy's wish, that she would not readily have accepted that Harry should die because her own life was being eclipsed. Such thoughts, however, serve simply to restart the tears. I prefer to think of them in their prime, Mandy a centre of sublime stillness while Harry worked like a tornado, writing and illustrating books which will find readers as long as they exist. "In later years," says book designer James Hutcheson, who collaborated with Harry on many projects, "I found myself reading his books to my own children at bedtime. It has been a delight to witness his art, weaving its magic from Scotland to the North Pole and ever onwards."