A miniature Sherlock Holmes book written exclusively for Queen Mary's dolls' house is to be published for the first time in its original format.
Sir Arthur Conan Doyle penned the story by hand in a tiny tome measuring 1.5in (3.8cm) by just over 1in (3cm).
It is a little-known tale written in 1922 in black ink over 24 pages, about how Dr Watson tries out his powers of deduction on Holmes - only to get things completely wrong.
How Watson Learned The Trick is one of more than 200 tiny books produced by some of the most famous British authors of the early 20th century for the dolls' house - on permanent display at Windsor Castle.
Other contributors include Thomas Hardy, Rudyard Kipling, Sir James Barrie and Edith Wharton.
The text of the story has been published before but the new miniature book is the first time it has been reproduced in a tiny format.
In the minuscule novel, Watson downplays the crime sleuth's skills over breakfast, telling him "I was thinking how superficial are those tricks of yours" and goes on to describe how his methods "are really easily acquired".
He deduces from the stubble on Holmes' face that he was too preoccupied to shave that morning and states that the detective has taken to financial speculation as he was interested in a newspaper's business page.
And the fact that Holmes is wearing a black coat and not his dressing gown proves he is expecting an important visitor.
But Watson is proved wrong - Holmes could not shave because his razor had been sent away to be sharpened, he was reading the cricket page next to the financial reports, and he put on his coat as he had an appointment with his dentist.
Oliver Urquhart Irvine, librarian at the Royal Collection Trust, said: "Sherlock Holmes is a world-renowned literary figure and an enduring character, who remains as popular today as in the Victorian society that Conan Doyle characterised.
"I am delighted that for the first time this Sherlock Holmes tale will be available in the exact format that Sir Arthur Conan Doyle produced nearly 100 years ago."
How Watson Learned The Trick is published by Walker Books in collaboration with the Royal Collection Trust on October 2, price £12.99.