Meghan Markle, the Duchess of Sussex, has appeared to dismiss serious allegations of bullying against her as an "attack on her character".
At the time, the Sussexes were living at Kensington Palace and Knauf was said to be concerned for the welfare of his staff working under her, writing in his complaint: "I am very concerned that the Duchess was able to bully two PAs out of the household in the past year."
Knauf added: "The Duchess seems intent on always having someone in her sights. She is bullying Y and seeking to undermine her confidence. We have had report after report from people who have witnessed unacceptable behaviour towards Y."
The couple have since relocated to California, citing a desire to get away from press intrusion, and have started to forge a career in the entertainment industry with big-money Netflix and Spotify deals.
Responding to the allegations, a spokesman for Markle said: "The duchess is saddened by this latest attack on her character, particularly as someone who has been the target of bullying herself and is deeply committed to supporting those who have experienced pain and trauma.
"She is determined to continue her work building compassion around the world and will keep striving to set an example for doing what is right and doing what is good."
The claims come before the broadcast of the couple's highly-anticipated TV interview with Oprah Winfrey.