Naturalist who was set free by Peter Rabbit

When Helen Beatrix Potter died in December 1943, she left a legacy of more than 4,000 acres of Lake District hill farms and woodlands to the National Trust. She had begun to acquire these holdings in 1905, when, as a 30-year-old spinster, she bought Hill Top Farm at Near Sawrey: 34 acres overlooking Esthwaite Water. Hers is a story not simply of a love of nature, but one anchored in an even stronger sense of place, a pure joy in the Lake District hill country. This was the only world in which she was free and in control of her destiny, and even that came only in middle age.

Linda Lear has produced an enormous book that authoritatively documents Beatrix Potter's world. But a chronicle of dates and events is not a "life" - that requires capturing something that here remains elusive. We see only glimpses of the development of an enormously talented and complex personality.

Under an early timidity, the future author of those wonderful children's tales had arrogance and some of her mother's snobbery. Of the knighthood of her uncle, the chemist Henry Roscoe (who indeed comes across as a pompous ass), she wrote: "How it makes us laugh." As a major landowner in the Lake District, she opposed incursions of industry and the railways but also fought the introduction of gas lighting to her own properties. Tenants in her properties were not given indoor WCs. She encouraged the Brownies and Girl Guides and headed the local district nurses' association but opposed women's suffrage.

Beatrix had a privileged but unhappy childhood. Her parents came from Manchester families that had grown wealthy in the textile trade but moved to southwest London, where Rupert Potter - a barrister keen on photography and drawing - and Helen Leech Potter made a home in Bolton Gardens. As Unitarian dissenters, the family lived at the edge of London society, which perhaps whetted the sharp edge of Mrs Potter's snobbery. Beatrix grew up with few friends. Governesses and tutors gave her an excellent education, although it was clear that her mother never intended her to have a life of her own. Her engagement at 39 to her publisher and editor, Norman Warne (in "trade"), was bitterly opposed; tragically, he died just a month later. Her younger brother Bertram (an alcoholic landscape painter) was married for 11 years before he dared tell his parents he had married the daughter of a wine merchant.

Entrapped in her duty to her parents, one constant sustained her - love of the outdoors. Every summer, her parents rented country houses, in the Lake District and the Scottish Lowlands. Summers became a magical time when she was uncharacteristically given freedom to roam the countryside on a pony and engage in her private fantasies. Natural history was a passion; even in the supposedly repressive London establishment the two children were allowed to keep a most unusual menagerie, including bats, newts, hedgehogs, mice that Beatrix tamed and a succession of rabbits.

From early on, she kept a diary in code. She also kept the drawings and watercolours that document a developing talent as an artist, encouraged by tutors, her father and even the painter Millais. But her maturation as an adult was slow and not helped by nearly two years of illness due to rheumatic fever. The result was a woman of intelligence and ambition but with a child-like quality. A photograph taken when she was about 26 sums up this first, repressed, part of her life - it shows a grown woman taking a walk with a bunny rabbit (Benjamin) on a leash like a dog.

The unhappy mixture of personal characteristics is well demonstrated in her attempts to make a mark in the world of natural science. Her skill as a scientific illustrator had led her to the Natural History Museum and the Victoria and Albert Museum, where her talent was appreciated. Tellingly, however, she needed more and, in frustration, disdained the curators. "They have reached such a pitch of propriety that one cannot ask the simplest question." She sold some designs for cards to a publisher and was commissioned to make a series of illustrations of insects. She also developed an interest in fungi, encouraged in part by the Scottish naturalist postman Charlie McIntosh (model for the immortal Mr McGregor), whom she met on summer visits to Dunkeld, Scotland.

Soon she was delving into aspects of fungal life history that were poorly known by professional botanists. Working by herself, she came up with three important ideas: that large fungi such as mushrooms and toadstools grew from a subsurface mould, or mycelium (which she demonstrated by growing the spores of mushrooms); that many fungal types hybridised with each other; and, finally, that the then-enigmatic lichens were composite organisms, a symbiotic combination of a fungus and an alga. None of this was completely new, but it was unconventional.

To take her ideas further, she needed to find help at the Royal Botanic Gardens, Kew. But her approach to Kew foundered in a disastrous mixture of clumsiness and timidity, made worse by Roscoe (then vice-chancellor of the University of London) and her father. She started with a low opinion of George Massee, the one person on staff who might have helped her (and later did), and alienated the director, William Turner Thiselton-Dyer, who unsurprisingly did not immediately agree with the woman who came in and told him that the ideas of his staff were wrong. "I informed him that it would be in all the books in ten years, whether or no, and departed giggling."

In fact, it is hard to see how any person lacking scientific qualifications would have got a welcoming reception in such a bastion of conformism.

Potter stuck at it, however, winning Massee round to her views, and he eventually sponsored the submission of a paper on her ideas to the Linnean Society. But she then withdrew it. And that was the end of her scientific endeavours.

Five years later, Potter published The Tale of Peter Rabbit and, with increasing financial independence, began her career as bestselling author, landowner and conservationist. Despite her growing wealth and properties, however, it was not until the death of her father in 1914 that she actually left home and lived year-round in the Lakes. She moved her mother there and launched herself fully, with the loving aid of William Heelis, whom she had married the year before, into a life on the land.

One of the things missing from this biography is a reckoning of Potter's finances, so central to her growing independence. The author even miscalculates the initial royalty rate for Peter Rabbit . Potter's difficulties in getting accounts from Harold Warne (eventually arrested for embezzlement) and her efforts to keep the publishers afloat are discussed without our learning just how much her books and related products actually earned.

But much more is missing: for example, any deep understanding of her family life and the characters of her strange parents. Regrettably, Lear does not let her subject speak for herself; the famous diary, for example, is rarely quoted. In the end, for this reader, there was great frustration in reading so much detail of Potter's life, so carefully and impartially recounted, but with so little insight into the gifted, contradictory woman herself.

Keith Thomson is professor emeritus of natural history, Oxford University.