The copy, which is being sold by a relative of Alexander's, is expected to fetch up £4,000 when it goes under the hammer in an online auction - the date of which is yet to be confirmed because of the coronavirus outbreak.

It includes corrections by Dahl in pencil, including two instances where Dahl has amended 'Barry' to 'Gus', and an arrow with the word 'No' pointing to a colour illustration of a gremlin next to a teapot.

Jim Spencer head of Hansons' Library Department, said: "The provenance for the item is established by descent from John Alexander to our vendor - who believes Alexander provided some inspiration for the plot.

"Most authors draw from their personal experiences and Dahl served as a pilot in the Second World War. The book was written for Walt Disney Productions in anticipation of a film being made but this never happened for various reasons.

"For any Dahl fan, and there are millions worldwide, this book is a remarkable collector's item. Not only does it take us back to Dahl's early days as a published author, that personal note provides an insight into the warmth of his character and regard for a wartime friend."

Dahl joined the RAF in Africa in 1939, and was badly hurt when his plane crash-landed in the Libyan desert a year later. He was discharged from hospital in 1941 and became a fighter pilot, taking on the Luftwaffe above the skies of Greece until severe headaches caused him to be invalided home.

He was subsequently sent to the British Embassy in Washington to help make the case for US involvement in the war in Europe, and became involved in sending intelligence back to London.

While in the States, the writer C. S. Forester - who penned the Hornblower series and was working to aid the British war effort - asked Dahl to provide details of his RAF experience in North Africa, including his crash landing, which Forester hoped to use for an article in The Saturday Evening Post. Instead of the notes which Forester expected, Dahl sent a finished story - for which he was paid $900, a considerable sum of money at the time.

The work led to The Gremlins, initially serialised in Cosmopolitan magazine, and a commission by Walt Disney for a feature-length animated film adaptation. The book publication consisted of a 50,000 print run for the US market, with Dahl ordering 50 copies for himself as promotional material, which he handed out to everyone he knew - including the British Ambassador in Washington Lord Halifax, and the US First Lady Eleanor Roosevelt, who read it to her grandchildren.

It was considered an international success with 30,000 more copies sold in Australia, but initial efforts to reprint the book were hampered by a wartime paper shortage. Copyright issues and the complicated involvement of the British Air Ministry delayed development of the proposed film, and after a year of story conferences and related research, Dahl realised that his book would be the only tangible product emanating from the project, despite Disney himself having a personal interest in The Gremlins.

However, the incident failed to halt Dahl's career. He continued to write, selling a string of short stories to newspapers and magazines, with his next children's book - James and The Giant Peach - being published in 1961.

A series of books that went on to become children's classic followed, including Charlie and the Chocolate Factory, Fantastic Mr Fox, Danny, the Champion of the World, The Twits, The BFG, and Matilda. Dahl's final book, The Minpins, was released in 1991, a year after his death. In total, Dahl's books have sold around 250 million copies worldwide.