Spoiler alert…sort of. Since, you know, history. But we will see the disintegration of Princess Margaret (Vanessa Kirby in seasons one and two, Helena Bonham Carter in season three) and photographer Antony Armstrong-Jones' (played by Matthew Goode in season two and Ben Daniels in season three) tumultuous marriage.
The show's history consultant Robert Lacey told Town & Country, "We'll see the breakup of this extraordinary marriage between Margaret and Snowdon. This season, you see how it starts, and what a strange character, a brilliant character Snowdon was."
In case you were curious: the pair divorced in 1978. (Quite controversial at the time.)