A "unique" archive revealing the workings behind a real-life treasure hunt book that became a global phenomenon is to be auctioned.
Artist Kit Williams' book Masquerade contained clues in paintings pointing the way to a buried golden hare.
Its publication in 1979 sparked an international search for the treasure.
The collection of notes, sketches and designs for the book are expected to fetch up to £15,000 at Sotheby's in London.
Philip Errington, from the auction house's books department, said the "absolutely unique" archive offered an insight into "a publishing phenomenon".
He said: "We rarely get the complete picture of literary work, art work, the thinking, the notebooks.
"Everything that Kit Williams put on paper, and that is still extant, is in this lot."
The collection includes a 112-page book of sketches and notes, showing how Mr Williams devised the riddles that perplexed a worldwide audience for years, as well as more than 50 pages of preliminary drawings and a mint-condition first-edition copy of Masquerade.
There are also photographs of the hare being cast in gold, and correspondence between Mr Williams and his publisher.
The sale is being held in the 40th anniversary year of Masquerade's publication, during which fans have organised a series of events.
Dr Errington said it was the first time Mr Williams had gathered the notes - which have been "in his study for years" - together as an archive.
The paintings in the book contained a series of riddles and puzzles, which ultimately pointed towards the site of the buried treasure - Ampthill Great Park in Bedfordshire.
The search captured readers' imaginations, with airlines offering special transatlantic flights to the UK for treasure-hunters, and farmers putting up signs warning people not to dig on their land.
The puzzle was finally cracked, in 1982, by a pair of physics teachers.
However, the prize was controversially claimed by a man who had links to Mr Williams' ex-girlfriend - a result which, when revealed years later, left the artist feeling "conned".
- 5 April 2019