She once told how her biggest worry in life was running out of money.Yet Dame Jilly Cooper - who died unexpectedly this week after a fall - is estimated to have left behind a staggering £10million fortune, the Daily Mail can reveal.The undisputed queen of the ‘bonkbuster’ sold more than 11 million books in the UK alone during her prolific career as one of Britain’s most-popular female authors.Dame Jilly’s best-selling romps portraying the scandals, betrayals and fabulous lifestyles of the horse-loving country set earned her in excess of £5million.Her work reached a new generation of fans after Rivals - one of her biggest-selling books - was turned into a smash hit Disney+ series, providing another £2million windfall for the writer.And the author’s wealth was boosted by astute property dealings with the 14th century home she bought in the Cotswolds for just £145,000 in the 80s now worth £3million.Dame Jilly was on the brink of having the property repossessed while she was writing Riders - the first in the series of 11 Rutshire Chronicles novels which turned around her fortunes.She once said: ‘We were always broke and worried about money. But then Riders got published. Dame Jilly’s best-selling romps portraying the scandals, betrayals and fabulous lifestyles of the horse-loving country set earned her in excess of £5million Jilly Cooper with her daughter Emily Tarrant (left) and son Felix Cooper (right) and his wife, when the acclaimed author received a Damehood at Windsor Castle last year‘Obviously, the bank manager had been sent a copy and so he came down for the weekend.‘He sat on our terrace and said, "Lovely old property this. What a tragedy you have got to sell it and don't think your dirty little book will get you out of it".’The book, published in 1985, went straight to number one in the bestseller lists.It became the first of Dame Jilly’s novels to be adapted for TV with a combined audience of 24 million viewers turning in for the two-part ITV mini-series - and launched her on the road to fame and fortune.But, haunted by the memory of nearly losing her home, she told The Sunday Times in 2020 that her ‘only real worry’ had always been money.She said: So I know it sounds silly, but I worry about it running out.’In 1994, Dame Jilly was reportedly one of Britain’s highest-earning women after being paid more than £630,000 over 12 months in royalties and TV rights.One analyst told the Daily Mail: ‘Her brand of "bonkbuster" novels meant that from early in her writing career she commanded big advances with publishers knowing sales were sure to follow.’In the 80s she stepped into another league with the publication of Riders.‘It was the first in the Rutshire Chronicles series of books which put Jilly’s work into households across the UK and around the English-speaking world.‘From that point on her books commanded six figure up-front payments and have been earning her and publisher Penguin Random House millions in sales since.‘Numerous editions of the books have been published and there was even a 40th anniversary edition of Riders published earlier this year. Dame Jilly Cooper - who died unexpectedly this week after a fall - is estimated to have left behind a staggering £10million fortune Jilly Cooper pictured with her daughter Emily in 2012 Her manor house in Bisley, Gloucestershire, which she and her family moved into in 1982‘The series which also included novels Rivals and Polo is believed to have earned her in excess of £5 million.’Dame Jilly, whose father was a brigadier, earned just £6-a-week from her first writing job - as a junior reporter on the Middlesex Independent.She moved into public relations and as a copywriter but was sacked from 22 jobs before finally working in publishing.In 1961 she married Leo Cooper who was a publisher of military books.Unable to have children of their own, they adopted son Felix, 57, and daughter Emily, 54, who are now set to inherit their mother’s fortune.When the children were adopted they lived with their parents in a turn-of-the-century working man’s cottage in Fulham which Dame Jilly bought for £7,000 in 1968.In 1982, the family moved to their manor house home in Bisley, Gloucestershire - which is set in 14 acres of fields and water meadows in a Cotswolds location that would provide the inspiration for Dame Jilly’s raunchy novels.The third book in her series Polo was published in 1991 and went on to become the biggest selling hardback novel of the year.Dame Jilly has told how, after a lunchtime drinking session with Felix, she splashed out £100,000 buying a house in Fulham after receiving a 'staggering’ royalty cheque from the book.She went on later to describe the impulse buy as the ‘best financial move’ she had ever made.At the time, Dame Jilly’s marriage was going through a rocky spell after publisher Sarah Johnson publicly revealed in 1990 that she had been having a six-year affair with Leo.The couple reconciled and Dame Jilly continued her writing to fund their lifestyle and later Leo’s care after he was diagnosed with Parkinson's disease in 2001.And she didn’t stop after Leo died aged 79 in 2013. Dame Jilly wrote or helped to compile more than 40 books including 18 novels which she crafted on an old typewriter named Monica. Jilly Cooper and her husband Leo. He died in 2013 aged 79