Lady Catherine Mason Beaton

A blonde trophy wife, former swimsuit model and Nate's current love interest. He continues an affair with her despite her married status. She is also Lord Marcus Beaton's stepmother and holds the title of Duchess. She is known to be picky when it came to her stepson's girlfriends, frightening each one with her coldness and cruel use of words. Blair catches her in the act with Nate during her fake annual party to impress the Duchess, subtly insinuating blackmail on the Duchess, forcing her to accept Blair as her stepson's girlfriend. She aids Nate financially even after she gets caught with him by Blair. It is revealed in "The Ex-Files" that she was having an affair with her step son, Lord Marcus Beaton. She was caught by Vanessa who later told Blair, and Blair threatened them to tell everyone unless they leave the country. They do so and are currently living in Brighton. It should be noted that in real British peerage, the wife of a Duke is known as Firstname Lastname, Duchess of X and not Lady Firstname Lastname.