Since this show started, I've fallen down the rabbit hole of Hayley Atwell's performances. I really like her Mary Crawford in Mansfield Park (though I'm probably not supposed to) and I had no idea that she was Bess in The Duchess. But my favorite, so far, is her episode of Black Mirror.
It's not the most original storyline, but her performance is really moving. I'm so used to her playing these strong, worldly women that is was shocking to see her so fragile. I kinda wish it were a full-length movie, rather than a single episode.
Next on my list is Pillars of the Earth and Brideshead Revisited.
Also, I'm embarassed to admit how long it took for me to realize she plays the older version of Peggy in Captain America: TWS. I just assumed they hired a different actress.