Addressed to a Irish guardsman Private W Fitzpatrick it asks for news of the author's only son, 2nd Lieutenant John Kipling, who had been posted missing in action one month earlier.

Kipling wrote: "I am writing to ask if you are able to give me any information in regard to my son. . . who is reported as wounded and missing in the fight in the wood beyond the Chalk Pit Wood on September 27.

"I should be most grateful if you could tell me anything you may remember about the fight on that day, or if you are able to give me the names of any men who you think may be able to help me with information."

Tragically, 17-year-old John Kipling was already dead when the letter was written.

Kipling sent his son to war

John Kipling was one of millions who gave their lives in world war I

Rudyard Kipling was the author of many classic novels set in colonial India and also wrote the popular poem If.

His letter, written on 11 November 1915, marked the beginning of a long search to discover his son's fate. Kipling refused to belive his son was dead.

The search dominated much of the rest of his life and inspired many of his later poems, including My Boy Jack.

The author had used his influence to get his son a commission after he had failed the initial fitness because of poor eyesight.

His son John later died in action during the Battle of Loos on 27 September, 1915. Initially he was reported "wounded and missing" - but later details revealed he had died after suffering severe head and neck injuries.

His remains were not discovered and identified until 1992, 56 years after Rudyard Kipling's death.