Considered the most beautiful debutante of the 1930s, heiress Margaret Sweeny (Claire Foy) is in the midst of a divorce when she meets the dashing - and married - Ian Campbell, future Duke of Argyll (Paul Bettany).

Putting aside gnawing doubts about her marriage, Margaret continues with her plan to secure her claim to Inveraray Castle.

Battlelines are drawn as the Duke and Duchess of Argyll enter into a bloody separation, all played out in the white-hot glare of a ravenous press.