Her father, Maurice Roche, was friends with George VI while her mother, Lady Ruth Fermoy, was Lady in Waiting to the Queen Mother. Her birthday also happened to fall on the same day George V died.
At just 18 years old, Frances married 30-year-old Edward John Spencer at Westminster Abbey and was one of the youngest brides to wed at the venue, Tina Brown wrote in her 2022 book, The Palace Papers.
It marked the beginning of a somewhat difficult chapter in Frances’s adult life.
Her husband, though polite and friendly on the surface, she soon discovered to be an abusive bully who drank, Ms Brown claimed.
As the future heir to Althorp, ‘Johnnie’ needed a baby boy to continue the Spencer name and inherit the family fortune, though this proved to be a challenge to fulfil.
Frances gave birth to her first child – Lady Sarah McCorquodale – in 1955 and went on to have another daughter, Lady Jane Fellowes, in 1957.
‘In order to produce a male heir, he made Frances go through six pregnancies in nine years, of which only four were carried to term, and he resented her having any independent life,’ Ms Brown wrote.
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Frances Roche with her husband Edward John Spencer and their daughter Lady Sarah in 1955
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The couple on their wedding day at Westminster Abbey in 1954
Before Diana was born, Frances did give birth to a baby boy who sadly passed away several hours after birth.
It was heart breaking for the couple and Ms Brown told how John refused to allow Frances to see the infant, also named John. She would only discover years later he was born with ‘extensive malformation’.
‘She struggled from the bed and banged frantically on the locked doors of the nursery to which he had been snatched away,’ the former editor in chief of Tatler wrote.
Frances recalled: ‘My baby was snatched away from me and I never saw his face. Not in life. Not in death. No one ever mentioned what had happened.’
Some 18 months later, Diana was born and weighed a healthy 7lb 12oz. Despite this, there was a great sense of disappointment in the Spencer family that ‘the new arrival was not the longed-for male heir,’ Andrew Morton wrote in his 1992 book, Diana: Her True Story – In Her Own Words.
They hadn’t even thought of a girl’s name for the new arrival and it took the couple a week to settle on Diana.
Older relatives pushed for answers as to ‘what was wrong with the mother’, Mr Morton wrote, and why she was giving birth only to daughters.
At 23 years old, Frances was subjected to ‘intimate tests’ at clinics on London’s Harley Street to diagnose the problem, which she found ‘humiliating and unjust’.
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Princess Diana with her mother, Frances, at Charles Spencer’s wedding to Victoria Lockwood in 1989
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The couple the day before their wedding, Frances was 18 years old and John was 30
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Frances and John pictured together back in May 1955
It wasn’t known at the time that males actually determine the sex of the baby.
Eventually, Frances did give the Spencer family their much desired male heir and on May 20, 1964, Charles – now the ninth Earl Spencer – was born.
Referring to their struggles to have a baby boy in Mr Morton’s book, their son recalled: ‘It was a dreadful time for my parents and probably the root of their divorce because I don’t think they ever got over it.’
Despite having the family they wanted, the couple’s marriage broke down after Frances fell for wallpaper tycoon Peter Shand Kydd.
In 1969, her divorce was finalised and Frances went on to marry her lover. Having earned the nickname ‘the bolter’, a blazing custody battle commenced with John.
In the early days of the separation, Diana and her brother lived with their mother, whilst Sarah and Jane attended boarding school.
They eventually all went back to live with their father after Frances’s custody attempts proved unsuccessful and she moved to Scotland with her new husband.
The bitter split led to a complex relationship with her youngest daughter. As her brother previously recalled: ‘Diana used to wait on the doorstep for her, but she never came.’
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Frances and Diana watching the Wimbledon Men’s final in 1993
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Prince Harry, Diana, Eleanor Fellowes and Frances attending Charles Spencer’s wedding rehearsal in 1989
His mother was not, he said, ‘cut out for maternity’.
Frances’s second marriage ended in 1988 and she turned to religion, converting to Catholicism at the age of 58 and devoted the rest of her life to the Church.
She had a complicated relationship with Diana over the years and lived a quiet life after her daughter’s death in 1997.
Frances developed Parkinson’s Disease and brain cancer and passed away aged 68 on June 3, 2004, at her home in Scotland. Her funeral on June 10 was attended by her grandsons Prince William and Prince Harry.