Sarah, Duchess of York hopes her debut Mills & Boon novel will be adapted into a TV drama because “everything that’s written she can already see”, her co-author said.

The Duke of York’s ex-wife described the book – Her Heart For A Compass – as a “sweeping, fabulous, historical novel” set in the 1870s and said her heroine Lady Margaret is “a very rebellious lady”.

The book, which draws on Sarah’s own life journey and incorporates research into her ancestry, is a fictional account of the life of the duchess’s great-great-aunt Lady Margaret Montagu Douglas-Scott.

Sarah co-wrote the book with Marguerite Kaye, who has written more than 50 novels for Mills & Boon set in a variety of historical eras.

The pair appeared on ITV’s Lorraine show and when asked by guest presenter Christine Lampard if the book will become a TV drama the duchess asked Ms Kaye to reply, and she said: “Yes it definitely will.

“The way it’s presented in the book, the way in which Sarah’s describing scenes she’s like ‘I’ve got a filmic mind’ haven’t you. She’s like a director so everything that’s written she can already see – it’s off the page and on the stage I think.”

Asked to comment on the huge amount of attention the Duke and Duchess of Sussex have received, the duchess looked back to the pressures she and Diana, Princess of Wales faced.

She said: “Well, I think Diana and I went through enormous things, without social media, in the 80s, and we really went through a lot, Christine.

“It was really, really, very, very tough. And if she was here today I know that she would just be completely like an eagle, she would fly high and be so proud of her two sons and their wonderful wives, who have delivered amazing children.”

Sarah added: “And I think that if she was here she’d beat me to the bouncy castle because she always used to beat me in the running races.”

The book tells the story of Lady Margaret who is banished from polite society after fleeing an arranged marriage.

In a dramatic video trailer for the novel, the duchess said: “Lady Margaret defies the echelons of high society. She follows her heart. She is in search of what she believes is the truth of her own heart.”

I really feel this book marks a new phase of my life and a whole new chapter for me

In the trailer, which features clips of the duchess in period costume looking intensely at the camera and into the distance, Sarah asks: “Can you take yourself to Victorian times? And can you move into a place with the courage and the bravery of Lady Margaret and how she manages to do that?

“So come on this journey with me from the drawing rooms of Windsor, to the country houses of Scotland and Ireland, and then to the slums of London, and on, on across the seas to the hustle and bustle of New York City in 1870. It’s so exciting. Come, join us.”

Talking about her heroine, the duchess said: “There are some obvious parallels between me and my heroine, my great-great aunt, Lady Margaret Montagu Douglas-Scott: she’s a redhead; she is determined to make her own way in life; and like me she can be headstrong.

“She also takes up a career in writing, and works really hard for the charitable causes she cares so passionately about. But ultimately Her Heart For A Compass is a work of fiction, not an autobiography.”

Sarah said she is “so excited to be diving into” a second novel for Harper Collins and Mills & Boon, again with Ms Kaye as her co-author.

“I can’t reveal too much about the new book at this point, but it will be another period drama, and will build on the world which I have created for this first book,” the duchess said ahead of her TV appearance.

The duchess fell in love with the Duke of York and brought renewed vigour to the monarchy in the 1980s alongside Diana but struggled to come to terms with the disciplines of royal life.

Born Sarah Ferguson and nicknamed Fergie by the press, she once confessed: “I was hopeless from the start… they could never make me the perfect princess.”

She was cast out from the royals amid her “toe-sucking” scandal in the 1990s and fell deeply into debt.

In 2010 she was caught up in the cash-for-access scandal, offering to sell an introduction to her ex-husband for £500,000 to an undercover reporter posing as a businessman.

The Queen’s former daughter-in-law, who has previously written her memoirs, is the author of children’s books including the Little Red, and Budgie the Little Helicopter series, and was an executive producer of the 2009 historical film The Young Victoria.

She has been reading children’s books throughout the pandemic on her YouTube channel, Storytime With Fergie And Friends.

– Her Heart For A Compass published by Mills & Boon, HarperCollins Publishers, is out on August 3.