Sherlock Holmes and the mystery of the one-inch Watson

How Watson Learned the Trick was penned in 1922 by the detective’s creator Sir Arthur Conan for Queen Mary’s doll’s house and is now on display at Windsor Castle along with a number of other tiny tomes by famous British authors of the early 20th century.

In its 24 tiny pages, it tells the story of Dr Watson’s doomed attempts to replicate his friend Holmes’s powers of deduction after suggesting that they are "superficial” and “easily acquired".

In fact, all of Watson’s deductions prove to be incorrect – from the idea that the stubble on Holmes's chin shows he was too preoccupied to shave (his razor has in fact been sent away to be sharpened) to the suggestion that he is involved in financial speculation due to his apparent interest in a newspaper's business page (Holmes was actually reading the cricket report on the opposite page).

The text of the story has previously been reproduced as part of some obscure collections of Holmes adventures but remains a mystery to most readers and has never before been published in its pocket-sized form.

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 will be published on 2nd October, priced £12.99