With the fourth season of The Crown finally hitting Netflix this weekend (Sunday 15 November), fans in lockdown have happily stayed inside and settled down to tuck into the royal dramas of the hit series.

As the show enters the 80s, we know the key storylines ahead: Margaret Thatcher becomes Britain’s first female prime minister, Prince Charles and Princess Diana marry (with Camilla Parker-Bowles in the background) and Princess Margaret deals with the fallout of her chaotic divorce. And then there’s the Queen, dealing with all the turbulence of her family and nation in a radical new era. 

But there’s one particularly emotional episode about something unexpected and shocking that happened.

Episode seven focuses on the Queen’s two “hidden” cousins, Katherine and Nerissa Bowes-Lyon, who were born with severe learning difficulties and admitted to a mental hospital in 1941. They were the daughters of John Herbert Bowes-Lyon – the brother of the Queen Mother – and his wife, Fenella.

Infuriatingly, because of the deep stigma attached with mental health in that era, the sisters were listed in the 1963 edition of Burke’s Peerage – a reference book to the nation’s aristocracy – as having died in 1940, when in fact they were both still alive.

They secretly continued to live most of their lives in Royal Earlswood Hospital. Nerissa died aged 66 in 1986 and Katherine died aged 87 in 2014.

Katherine and Nerissa also had three other cousins in the institution with the same disabilities – Edonea, Rosemary and Etheldreda, who were the daughters of Fenella’s sister Harriet. The condition was thought to have been hereditary and descended from their common maternal grandfather, Charles Trefusis, 21st baron Clifton. 

The truth about all of this only became public knowledge in 1987 and there have since been mixed reports over which members of the royal family knew about the sisters. 

But The Crown has used a bit of artistic license to tell the story of what happened, suggesting that the Queen Mother knew about the girls from the start. 

The episode opens with images of the Queen arriving at the Royal Variety Performance being shown on a TV in a hospital. Katherine and Nerissa, who are in their 60s, stare at the screen, stand for the national anthem and stop only to take pills handed to them by a nurse.

It then shows Princess Margaret, who only learns of the sisters’ existence from a therapist who asks the royal if she is aware of any relations struggling with mental health issues. This leads to a confrontation between Margaret and her mother.

“Locked up and neglected. They’re your nieces, daughters of your favourite brother,” Margaret says. “It’s wicked and it’s cold-hearted and it’s cruel and it’s entirely in keeping with the ruthlessness which I myself have experienced in this family.”

The Queen Mother attempts to explain, asking: “Can you imagine the headlines if it were to get out?”

Although this conversation obviously never took place, it of course highlights a devastating storyline that attempts to honour the true lives of Katherine and Nerissa. 

You can watch season four of The Crown on Netflix now.

Images: Netflix/The Crown