From now on, look twice at any painting or print with fairies, goblins or dragons in it, especially if it is Victorian. It could be worth snapping up. As John Windsor explains, the next collecting boom could leave you with a fairytale ending.

There are fairies at the bottom of the next art investment boomlet. Sotheby's will be first into the magic circle with a bumper 326-lot sale of British Fantasy Art on 30 October, culled partly from a big private collection.

At the Royal Academy, an exhibition, Victorian Fairy Painting, opens on 13 November, the same date as a selling exhibition, Fairy Folk in Fairy Land, at the London dealer Peter Nahum's Leicester Galleries.

Paintings of fairies by Victorian artists whose names have hitherto been scarcely known at street level - John Anster "Fairy" Fitzgerald, John Simmons, Robert Huskisson - will rise in price.

So will fairy paintings by Victorians best known for other subject matter, such as those of John Atkinson Grimshaw. His paintings of dimly lit, squelchy suburban streets are worth up to pounds 200,000. His rarer fairy paintings, such as his Iris, Spirit of the Rainbow, on show at the Leicester Galleries, could now be worth pounds 120,000.

And there will be new interest in such characters as Richard "Dickie" Doyle, father of Arthur Conan Doyle, spiritualist and creator of Sherlock Holmes. Dickie was a household name in Victorian times. He designed the famous frolicking Punch magazine cover of 1849 and was a prolific illustrator of fairy tale books.

There are ink and watercolour works of his at Sotheby's at pounds 600-pounds 800. Mr Nahum disdains Doyle's skimpy sketches but is offering his full-colour original prints at pounds 500-pounds 600 and watercolours at around pounds 5,000.

Sotheby's also has pencil, ink and chalk sketches by Sir Joseph Noel Paton, a well-known illustrator of his day, rather bullishly estimated from pounds 400-pounds 600 for a lot of 10 to pounds 3,000-pounds 4,000.

There has not been such a major rediscovery of a collecting genre since Victorian painting itself came to the fore at auction in the late Eighties. Then, fairies were dismissed as peripheral to the artists' main oeuvre. Real flesh and blood, especially female and diaphanously draped, and busy genre scenes were the thing.

But the Victorians' fairies were not just meaningless ephemera. They were deeply embedded in their psyche. Fairyland offered a haven from the demands of scientific and technological progress, in which the occult and the erotic could flourish without disapproval.

Mr Nahum has discovered that some of their goings-on had symbolic meaning for Masons and Rosicrucians. A Sylph sprinkling early morning pearls of dew is likely to be the Rosicrucian spirit of the air for the Ros Crux, the dew cross. Fairies could become a lucrative quarry for collector-investors prepared to research the Victorians' fascination with the occult.

The craze for fairies had its heydey from about 1840, when spiritualism and table-rapping spread from America to Britain, until about 1870. But it remained a potent undercurrent in British painting and illustration up until the horrors of the First World War.

It is a peculiarly British genre. You can find echoes of Paton and Fitzgerald in the Pre-Raphaelites. Having seen the RA exhibition, visit the Tate's exhibition, "The Age of Rossetti, Burne-Jones and Watts: Symbolism in Britain 1860-1910" for comparison. Those three were away with the little folk.

Much of the seductive appeal of the Victorian artists' fairylands lay in their realism. The crowded fairy scenes of Doyle or Paton were just as believable as Frith's scenes of The Derby Day or The Railway Station. Add a whiff of opium, which fairy paintings occasionally hint at, and the jaded Victorians were off on a totally legit trip.

But if you hesitate to reach for your wallet, consider this: the Japanese are buying fairies. The wand that sparked the present proliferation of fairyology in London came from Kimie Imura-Lawlor, Professor of English literature at the University of Meisei, Tokyo.

She has accumulated a big collection of Victorian fairy pictures, some bought for her by Mr Nahum, has translated Conan Doyle and Joe Cooper's book on the Cottingley fairy hoax, and has published monographs tracing how Japanese literature began to adopt British fairies in the Twenties and Thirties.

Sotheby's auction: "Realms of the Mind: British Fantasy Art and Illustration", Thursday 30 October (10.30am). Leicester Galleries selling exhibition, "Fairy Folk in Fairy Land", 13 November-20 December, illustrated book pounds 10, pounds 12.50 with p&p, 5 Ryder Street, London SW1 (0171-930 6059).