Played by Oona Chaplin
Marnie auditions for a new role on a BBC cookery programme and gets it. Sublimating her desire for a family that so far has not happened, Marnie throws herself into her new career.
When scandal threatens to destroy not only her marriage to Hector but also both their careers, Marnie finds a renewed strength of character, and gives Hector an ultimatum that changes everything.
As well as appearing in The Hour, Oona has also starred in Sherlock and HBO's Game of Thrones.