The Crown season 4, episode 7 recap – what happened in “The Hereditary Principle”?

By Daniel Hart
Published: November 15, 2020 (Last updated: November 29, 2023)
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Netflix series The Crown season 4, episode 7 - The Hereditary Principle


“The Hereditary Principle” presents another Princess Margaret-centric chapter that is similar to its predecessors. The value of purpose and a sense of meaning is discussed, while also showing the cruel pitfalls of the Royal Family.

This recap of Netflix’s The Crown season 4, episode 7, “The Hereditary Principle” contains significant spoilers.

We recapped every episode — check out the archive.

The opening

The Crown season 4, episode 7 opens with Princess Margaret smoking and applying make-up — she seems to be getting ready for a night of socialising, and nothing seems have changed since Season 3. On TV, the Queen is attending an Entertainment Benevolent Fund. Meanwhile, a group of people in a mental facility are watching it all unfold on TV who become important later. The vibe gives away everything — Margaret is still trying to find purpose after being second fiddle all her life.

Slightly in love but a bad cough

Princess Margaret continues dancing and drinking — she’s in high spirits. She’s enjoying her time with a man named Derek Jenning, but he’s backing off despite a few months of fun and intimacy. Margaret tells her sister that she’s falling slightly in love with Derek. The only issue is, Derek is a Catholic Priest. Elizabeth notices that Margaret has had a cough for a while, and suddenly, she coughs blood.

Birthday celebrations

On the news, it’s revealed that Princess Margaret is having investigative surgery. In the mental facility, a woman named Katherine celebrates her birthday. As for the Royal Family, it’s Prince Edward’s birthday, and they are all celebrating. The scenes keep flitting from the Royal Family to the mental facility.

A sense of meaning

Princess Margaret tells Elizabeth that she wants to embark on a new chapter without men, cigarettes and alcohol. She wants to focus on her duty as a royal and asks Elizabeth for more responsibility — “A sense of meaning”. We’ve seen this scene before, and there’s the context in that we know how it played out for Margaret last time. It goes to show that the shackles placed on members of the Royal Family can remove purpose and meaning entirely.


Elizabeth speaks to Margaret about the 1937 Regency Act. She’s told to relinquish her role as the counsellor of state now that Prince Edward has turned 21. Margaret asks Elizabeth and her advisor not to take that away from her — she wants work, purpose and dignity. She’s afraid of time and how she has to fill it. Elizabeth tells her that they have to live with it, but Margaret stresses that she’s the only one having to live with it. There’s a lot of sadness in the room in this scene; it’s always two steps forwards and three steps back for the princess.

Charles gives Margaret advice

Charles visits Margaret, who has decided to take solitude at an exotic location. He tells Margaret that Diana is pregnant again which has brought more gloom — he explains how depressing it is and that he is now seeing a professional. Charles urges Margaret to see a professional as well.

A family revelation

Margaret tells her therapist she’s against counselling and believes she should “get on with it”. She admits that she has been feeling low for a while. The counsellor asks if any other members of the family have mental problems — Margaret learns from the therapist about her first cousins, Katherine and Nerissa Bowes-Lyon, who are in the Earlswood Institution for Mental Defectives. She raises this to Elizabeth, but the Queen believes they are dead. Margaret wants to check. Elizabeth proves that in the Royal books Katherine and Nerissa died long ago and Margaret finds that strange, which encourages her to embark on her own investigation — this is her finding purpose.

Investigating the institution

But sometimes finding purpose results in finding something you never wanted to know.

Margaret and Derek visit Earlswood Institution for Mental Defectives. She asks Derek to go inside and look for Katherine and Nerissa. Derek returns and confirms they are alive and that they know about the Royal Family. He then reveals that there are more cousins, equally afflicted.

Disgracing the family

Princess Margaret is fuming and speaks to her Queen Mother about the five family members locked away in a mental institution. Queen Mother explains they had no choice, but Margaret states that it’s cruel and it represents the family byline of “You don’t fit the perfect mould”. She thinks the family should be ashamed. And then we are reminded how Royal Families can be cruel — the Queen Mother explains to Margaret that their bloodline would have been under scrutiny and that the hereditary principle was on the line — the Royal Family needs 100% purity. She blames Uncle Jock. This is an indictment of Royal history — how those who do not fall in line, physically, mentally and socially are cast out. However, there’s a sense of hypocrisy, especially with how Margaret views Princess Diana.

Getting answers from the therapist

Margaret speaks to her therapist about how every misfortune is written in her blood. She asks if she’s destined to be mad too. The therapist denies that and states, “The genetic fault responsible for your cousins’ condition seems to have descended from their common maternal grandfather, Charles Trefusis, 21st Baron Clinton. This suggests that the recessive gene responsible for their condition lies with the Clinton family.” It ended up with their family through Aunt Fenella, who was married to Uncle Jock.

Margaret wonders why they were hidden away if it didn’t come from them — she thinks it’s unforgivable what their family did.

The ending

Derek tells Margaret to become Catholic, but she tells him she can’t because it would be frowned upon. Derek is frustrated with Margaret, who doesn’t want to distance herself from her family after learning that they locked up members. Margaret insists she’s at the centre of the family and she cannot just withdraw — she accepts she is part of the problem. She tells Derek that they cannot see each other again.

Margaret goes back to her exotic lifestyle; smoking, drinking and partying again. She has time to fill again, and the only way to drown out her fear is by losing control.

The end of the series confirms the cousins discussed in this chapter:

  • Katherine Bowes-Lyon — 4th July, 1926 – 23rd February, 2014.
  • Nerissa Bowes-Lyon — 18th February 1919 – 22nd January, 1986.

The Crown season 4, episode 7 presents another Princess Margaret-centric chapter that is similar to its predecessors. The value of purpose and a sense of meaning is discussed, while also showing the cruel pitfalls of the Royal Family.

Netflix, TV Recaps
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