10. Cri De Coeur (S310)
There have been a number of episodes across all series exploring the demise of Margaret, but none have been so utterly heartbreaking as this. The finale of Season 3 sees the beleaguered Princess hit rock bottom, her marriage all but over while her family comments on what a lovely man her husband is - at her birthday party!
There is another scandal awaiting poor Margaret, when she starts an intimate relationship with 'toyboy' Roddy Llewellyn. But just as there is a small glimmer of happiness in the Princess' life, the paparazzi catch her in the act and her 'scandalous' actions are plastered all over the front pages. We then watch as the hurt builds up inside Margaret, losing both husband and lover, until she can finally take no more.
The final scene between Margaret and the Queen is both captivating and illuminating, with Helena Bonham Carter and Olivia Colman at the top of their game. After making a strong focus throughout the season on the complete lack of emotion that Queen Elizabeth is able to display, her flowing tears at the idea that her sister nearly died reinforces how strong the bond between the sisters truly was.