In addition to Diana, who died in 1997, Sherborne has worked with celebrities including Elton John, Harry Styles, Paul McCartney, Amy Winehouse and Michael Douglas.
Sherborne will argue for Meghan in her action against Mail on Sunday and its publisher, Associated Newspapers, for their alleged misuse of private information, breach of data protection and infringement of copyright.
Meghan is suing the outlet and its publisher for publishing a handwritten letter she wrote to her estranged father, Thomas Markle, shortly after her 2018 wedding to Prince Harry.
Meghan's legal team plans to argue that the publishing of the letter was not only a violation of several laws, but that the Mail on Sunday cherry-picked portions of its content to manipulate readers.
Last week, a procedural hearing was held virtually in front of Justice Mark Warby, due to the coronavirus pandemic. Though no official date has been set for the trial yet, Justice Warby said that he hoped to make a decision on the hearing within the week.
The lawsuit isn't the only step Meghan and Harry have taken against the press. Earlier this month, they announced that they would no longer be working with four British tabloids -- The Daily Mail, The Sun, The Express and The Mirror -- for running "invasive" stories.
"While the world is engaged in a fight against COVID-19, Meghan and Harry are engaged in a fight against the British press," royal expert Katie Nicholl previously told ET. "They really are not backing down, they wrote to the newspaper editors of four major popular tabloid publications over here in the United Kingdom saying that they would have zero engagement with these publications."