The book could reveal the struggles that Meghan faced leaving her native Los Angeles for life as a member of the British royal family. One of the Duchess’s friends revealed to Mail Online that the former Suits star regularly wrote down her thoughts and feelings in the book.
If the diary were ever to be published it could provide unrestricted access behind the scenes of the monarchy.
This summer will already see the publication of Finding Freedom which will provide intimate details of Prince Harry and Meghan’s life together.
The existence of Meghan’s diary also piqued the interest of royal author Andrew Morton, who previously worked with Princess Diana on an autobiography.
He told the Mail Online: “She is a good writer, with a nice turn of phrase
“Remember she studied English in her first year at Northwestern College.
For Meghan being able to share her own narrative would also not just be financially beneficial.
“She would have total control,” added Mr Morton
Before marrying Harry, Meghan wrote her own lifestyle blog “The Tig” which was closed down not long before her engagement.
The Tig shared the Duchess’s favourite music, foods and fashion trends.
She previously penned a post on the blog about living independently and being comfortable “taking yourself to dinner”.
The royal even took herself on an Eat, Pray and Love type adventure where she spent a month attempting to “eat everything, pray (meditate ) often, and simply love my life, every once of it”.
This time of self-reflection occurred a few months after meeting Prince Harry when they were not public yet and may have been enduring a rough patch.
A lot of Meghan’s writing on her blog focused on sustainability, including “sustainable holiday celebration tips”.
It may be that her diary entries also elaborate on her green ambitions.
The Duchess is also rumoured to have written another blog anonymously when she was acting entitled The Working Actress.
She wrote: “My hair is primped, my face is painted, my name is recognised, my star metre is rising, my life is changing.”
Over the last century many royals have kept their own personal diaries, but never before have the contents been published.
The most revealing insights until now were often delivered by Princess Diana, who famously revealed her eating disorder and self-harm.
In 1992 Andrew Morton interviewed Diana where he uncovered Prince Charles and Camilla’s affair.
The book was composed of tape recordings that Diana made.
Morton said of the biography written with Diana’s co-operation: “It soon became apparent that the book really was, as it claimed, Diana’s own true story.
“And the Princess quickly began to receive the kind of support that always meant so much to her.
“Letters came flooding in — many from people who’d suffered from eating disorders themselves.’ He added.