A WEEK tomorrow will see me at a Harrogate hotel, scrabbling through books. Scrabbling not for slightly foxed Agatha Christies in the town where the lady hid during her 1928 disappearance, but doing some detective work of my own in pursuance of my latest Mr Toad-like enthusiasm.

Because, gloriously and in previously near-complete ignorance of this major icon of north-country heritage, I have stumbled upon Thomas Bewick, the master wood-engraver to the doors of whose Newcastle workshop the cognoscenti beat a path in the late 18th century and the early 19th.

And if there aren't examples of his art at the do being held at the Crown Hotel - down the road from Agatha's Old Swan - by the provincial booksellers' fairs association, then ... well, I shall sue them under the Trades Descriptions Act.

For is this not the Illustrated and Children's Bookfair? Then, by definition, there must be something there by the father of modern book illustration, a man whose earliest great work was the exceedingly rare The Youth's Instructive and Entertaining Story Teller (1774).

Bewick's prowess, and the fascinating tale attached to it, was brought properly to my shamefully blinkered notice by Mr Brian Alderson, a Richmond man who has been children's books editor of The Times and who is president of the Children's Books History Society. Next month he's in Toronto to lecture on the latter specialty; more to the point, he's a founder member of the Bewick society, the brainchild of Mr Frank Atkinson, the man who went on from the Bowes at Barnard Castle to create the Beamish museum.

For the Harrogate book fair, as well as assembling an exhibition to mark the centenary of Edward Ardizzone, who illustrated the stories and poems of authors as diverse as Graham Greene, Betjeman and Trollope, Mr Alderson is helping with a display of historic children's books taken from a collection held by Harrogate public library.

When we spoke before he got down to the final choice from that collection, I urged him to look out for such as Tommy Trot's History of Birds and Beasts, (or A Pretty Book of Pictures for Little Masters and Misses) 1779, in which the young Bewick drew animals to illustrate poems and prose written earlier by, almost certainly, Oliver Goldsmith.

But he was a bit pre-occupied by not being able to find, for the moment, what he had hoped was going to be a star of the display: Marmaduke Multiply's Merry Method of Making Minor Mathematicians (circa 1810 with hand-coloured engravings).

Outside the pages of 1930-50s comics - and apart from a recent chairman of the BBC, Duke Hussey - you don't come across many Marmadukes, of the multiplying variety or otherwise. So it is a bit of a coincidence to find that a real-life Marmaduke played an important part in the prolific Bewick's rise to fame.

Three publications largely ensured his major reputation in book-illustration: A General History of Quadrupeds 1790, with 101 pictures of animals worldwide; and two called History of British Birds, the first (1797) with 117 pictures of land birds and the second (1804) with 101 of sea birds; all three went into several editions.

Charlotte Bronte, who had her heroine reading one of his British Birds volumes just before some small domestic tragedy in Jane Eyre, wrote a poem to his memory a few years after his death in 1828. It has been said of the Bewick birds: 'They seem almost to utter their cries; they are glossy with health and freedom ... are alive."

On top of his artistry, which ranged from banknote design to bookplates, he was also no mean naturalist; he edited the text which accompanied the Quadrupeds and the land birds pictures, and when the celebrated French-American ornithologist Audubon visited Britain he went out of his way to meet Bewick. Then there is his discovery of a previously unrecorded sub-species: the Bewick's swan, a winter visitor here from Arctic Siberia. That's a different one, he must have said, it's smaller and the yellow splash on its beak is round.

He was wearing his naturalist's hat when he joined an 1824 campaign against some project which objectors argued would further degrade the Tyne as a salmon-fishing river. When he was a child, he said, his farming parents would send him (from near Ovingham, Northumberland, where his first home, Cherryburn, is now a National Trust property) to Eltringham ford to buy salmon from fishermen at between a penny and tuppence a pound; apprentices had it in their indentures that they would not be forced to eat salmon more than twice weekly.

The artist made his engravings from his own drawings and watercolours, hundreds of which are held by the Hancock Museum at Newcastle but seldom displayed because previous exposure began to fade them. A Bewick room at the museum includes a re-creation of his workshop in St Nicholas' churchyard.

Many of these originals were done by Bewick at Wycliffe Hall, on the Tees downstream from Barnard Castle, of one Marmaduke Tunstall, an enthusiastic naturalist who had put together at Wycliffe his own museum of animal and bird specimens; in 1791 Bewick spent two months working at the hall. The two men had had business together in 1788 when Tunstall commissioned from Bewick what was to be regarded as a masterpiece among his engravings, that of the Chillingham wild bull of the famous herd of white Caledonian cattle in deepest Northumberland.

Tunstall's natural history collection eventually became the core of what is now the Hancock Museum. Intriguingly, it did so only after passing through the hands of another of Bewick's contacts, George Allan of Blackwell Grange, Darlington. Allan, an antiquary who had his own press, bought the collection on Tunstall's death and when he himself died it was acquired by Newcastle literary and philosophical society, largely at the instigation of Bewick and his friends.

(The Tunstalls had been at Wycliffe since 1605 when an earlier Marmaduke married into the ancient Wycliff family and 160 years later it was our Marmaduke who turned their fortified farmhouse into today's Wycliffe Hall. There's a literary ring to the name of this year's new owner of the house: he of the burgeoning drugstore chain Savers, a Mr Tonks - rather Dickensian, don't you think?)

Bewick also stayed at Blackwell Grange, a visit mooted in a 1797 letter in which the engraver thanks George Allan for some books and says that he had been overwhelmed not only by work but also by making arrangements to strike out on his own after a long and usually happy partnership with the man to whom he had been apprenticed for seven years at the age of 14; in addition he had been standing in as Newcastle's overseer of the poor.

The Darlington stay the following spring enabled him to fulfil a commission from "the Durham Agricultural Gents. in taking drawings of their best and worst sheep, horses, bulls, cows etc." But his employers found the results too lifelike. Bewick would not give the animals "lumps of fat here and there, where he could not see it" solely to please "fat cattle-makings." He said: "I got my labour for my trouble."

Another Darlington connection: in 1884, Edward Mounsey, a prominent Quaker in the town, paid 100 guineas for a two-volume set of British Birds which had notes handwritten by the engraver, and the same man also acquired the antlers of a reindeer which had been drawn from life by Bewick after being brought back from Lapland in the 1780s by some of his wealthy Newcastle patrons.

There was a touching coincidence at the time of Bewick's death, aged 75. Only a week before, he had put the finishing touches to his largest woodcuts, one which ranks with the Chillingham bull as one of his finest works. It was called Waiting for Death and it was an enlarged and vastly more detailed version of the subject of his first known sketch as a boy.

The picture is of an emaciated old horse standing in the rain next to a withered oak tree. Bewick wrote a moving piece detailing the animal's decline from glory years as a general's steed to being abandoned by his impoverished final owner: "... having faithfully dedicated the whole of his powers ... to unfeeling man, he is at last turned out, unsheltered and unprotected, to starve of hunger and of cold."

He had intended the woodcut to be one of two or more, to be printed one on top of another to add effects such as rain and further shading. So, effective as the single woodcut was, the result is not as the artist intended. In a scholarly essay written in the 1880s by the Rev William Kingsley, rector of South Kilvington, Thirsk, a Bewick admirer and an art critic, which explains the techniques pioneered by his hero and concludes of his final work:

"Much as we regret the unfinished state of the engraving, it ought to be a satisfaction to all who look at it to remember" that the artist died in harness; and, unlike the poor horse, "his eye was not dim, nor his natural force abated."

l The book fair in Harrogate on Saturday, October 28, 10am-5.30, admission £2, is organised by Mrs Gill Tiffin, of Coniscliffe Road, Darlington, tel 01325 487274. The original of the fair's logo drawn by Ronald Searle is to be sold by silent auction in aid of the National Literary Trust.