Thomas Lyon-Bowes, quite cruelly, became known as the Monster of Glamis with the tragic birth of this heir feeding the imagination of Victorian story tellers, local gossips and likely even giddy aristocrats keen to entertain their guests after dinner.
What is known is that Thomas was born on October 21, 1821 at Glamis Castle in Angus with the official records stating the baby boy died on the same day.
His parents were Thomas, Lord Glamis, son of the 11th Earl of Strathmore, and Charlotte Lyon-Bowes.
The couple were the great, great grandparents of the Queen Mother, who was also born at Glamis - as was her daughter, Princess Margaret.
Rumours started circulating in villages around Glamis Castle about the supposed death of young Thomas, which were likely fuelled by reports of an unnamed midwife that Thomas had survived the birth.
An apparent lack of gravestone for the boy probably supported the suspicions surrounding his fate.
Over time the story grew. Allegedly a workman who had encountered Thomas in a passage close to the chapel was offered money by the Earl to emigrate to Australia.
Also appearing in later versions of the tale was an estate manager who refused to step foot in the castle after being told about the purpose of the secret chamber.
The story moved rapidly into the public arena not just in Scotland but in Europe and North America.
Sir Walter Scott wrote of an “eerie” night at Glamis in which he referred to the secret chamber - although no monster - in 1830.
A version featuring the monster appeared in the New York Times in 1864.
The 1908 edition of Notes and Queries, published by Oxford University Press, goes into great detail about the “Mystery of Glamis” with the writer claiming he had known the story for 60 years.
The account said the “general verdict” was that the legend “was so well established and interesting that it was almost impious to attempt to explain it away.”
It said: “The story was, and is, that in the Castle of Glamis, the celebrated old castle of the Earls of Strathmore, is a secret chamber.
“In this chamber is confined a monster, who is the rightful heir to the title and property, but is who is so unpresentable that it is necessary to keep him out of sight and out of possession.
“The secret is supposed to be known to three persons only - the Earl of Strathmore, his heir and the manager of the estate.
“This terrible secret is said to have a depressing effect on the holder of the title (who, if the legend we exact, would not be in possession lawfully of either title or property) and on his heir.”
A group of guests allegedly went to search for the heir, according to later accounts, by hanging towels from all the rooms they could enter in a bid to find the secret chamber. After going outside to look at their markers, it is claimed that one window was still empty.
They could not find the corresponding room inside.
Depictions of the mysterious earl also emerged in time. Jacynth Hope-Simpson in her book Who Knows? suggested the boy may have suffered a genetic defect given the child’s parents were cousins first removed.
Ghost writer Peter Underwood suggested Thomas had wasted arms and legs and resembled “an enormous flabby egg.”
Historian Mike Dash, who writes for the Charles Fort Institute, also wrote of a “second puzzle” of the Glamis legend that emerged during the 19th Century.
Far from being home to an unwanted heir, the secret chamber contained the remains of members of the rival Ogilvy clan, who came from lands at nearby Kirriemuir.
After seeking refuge at Glamis, they were allowed in the property and shown into the chamber, where they were barricaded in and starved.
Dash wrote: “ Their skeletons, still scattered on the floor, were the secret that the Lyons family was so anxious to conceal.
While the true nature of the mystery of Glamis remains unexplained, it does appear true that the castle was burdened with a particularly dark secret.
Claude Bowes-Lyon, the grandfather of the Queen Mother, who inherited the Earldom in 1865, reportedly said: “If you could even guess the nature of this castle’s secret, you would get down on your knees and thank God it was not yours.”