Frances Griffiths and Elsie Wright caused a global sensation when they faked snaps of fairies in 1917.

But Frances always maintained that one image - less distinct than the rest - wasn't a hoax.

Now this photo, part of a fresh Cottingley Fairies treasure trove, is to go under the hammer at auction next month, the Telegraph & Argus can reveal.

And Bradford's National Museum of Photography, Film and Television - which on Friday took possession of the cameras used in the famous hoax - could enter the bidding.

The saga of the Cottingley Fairies has gripped the imagination of people around the world since a film version of the affair, Fairytale - A True Story, was released this year.

The girls photographed paper cut-outs of fairies, held up by hatpins, at Cottingley Beck as a joke - but their prank got out of hand when leading writer Sir Arthur Conan Doyle was fooled, writing a book about it.

The original cameras used by the schoolgirls are now back on public display in Bradford after readers backed a joint cash appeal by the Telegraph & Argus and Amateur Photographer Magazine.

Now, Frances' daughter Christine Lynch has decided to sell more material relating to the story at auction at Sotheby's on Thursday, July 16.

Going under the hammer are a signed first edition of Conan Doyle's book, The Coming of the Fairies, and valued at £3,500-£4,500; and a boxed set of 37 glass slides of the fairy pictures (valued at £4,000- £5,000).

Christine Lynch, of Belfast, who recently paid an emotional visit to her mother's fairy-inscribed gravestone at Scholemoor, said she would be very happy if the heirlooms ended up at the National Museum.

"One of the glass slides shows a picture that my mother always insisted was genuine," she said. "It is a beautiful picture, the very last one.

Alison Jarman, spokesman for the National Museum of Photography, Film and Television said: "This is material we are very interested in because it's a local story, and it's got such international interpretation and interest.''

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