When she started to do her research she stumbled upon a mystery that had been hidden for many years, once she started to delve, she came across a story that has now become the focus of this book - a completely different book to that which she had planned, but one that is incredibly detailed and often reads like a fiction novel.
In the opening chapters, the ninth Duke of Rutland; John Manners is dying. For the last few years of his life he has shut himself away in the 'secret rooms' amongst the servant's quarters on the ground floor of Belvoir Castle.
These rooms were cramped, with no luxuries at all, so different from the sumptuous suites on the upper floors of the Castle. After John's death, his son sealed off the rooms and until Catherine Bailey arrived to do her research, no one else had entered them.
The Duke was a strange and solitary man throughout his life, he collected and catalogued items constantly including birds eggs, photographs, and most importantly, the family correspondence going back hundreds of years. As the author carefully made her way through the thousands of letters kept in the rooms, she found that there were three periods of John's life that were missing, these were from 1894, 1909 and 1915. Everything else had been carefully catalogued including the estate accounts, so what had happened to John during these times of his life that he was determined to erase?
John was the second son of Henry, the 8th Duke of Rutland and his wife Violet. Their first born son Haddon tragically died at the age of 9. Haddon's death occurs at the time of the first batch of missing correspondence in 1894. John, aged just 7 at the time, was sent away from home immediately after the funeral to live with his Uncle Charles - his mother Violet could not bear to look at him and Haddon was deeply mourned by his parents.
Violet's apparent cruelty, neglect and lack of compassion to her second son continues throughout his life, not once did his parents visit him when he was sent away to school and it was not until he was due to go to France as an Army officer in the Great War that they began to take notice of him again. It was not that they feared for John's safety, it was purely because they needed the Rutland name to be continued and the Belvoir Estate to remain in the family.
Violet's manipulating and pressurising of leading Army figures is astonishing to read, she comes across as a driven and hard-faced woman who will stop at nothing to get what she desires. John's father Henry was a weak man, more concerned with appearances than with his son's feelings.
It is no wonder that John grew to be a damaged, vulnerable and needy adult. A man who found it difficult to love and to be loved and preferred to surround himself with inanimate objects and who was determined that no one would find out the family secrets. And there are so many secrets uncovered in this story; just how did little Haddon die? Where exactly did John spend most of the war years?
The book is beautifully presented, with a detailed family tree, black and white photographs and a plan of Belvoir Castle.
The Secret Rooms: A True Gothic Mystery will be published by Penguin on 1 November 2012.