Rebekah Brooks, the former editor of the News of the World and the Sun tabloids, has been found not guilty of approving a payment to a public official for a photo of Prince William.
Brooks, who rose to become chief executive of News International, Rupert Murdoch's British newspaper division, still faces four other charges in the trial, including for phone hacking.
After three-and-a-half months of prosecution argument at the Old Bailey court in London, Brooks was due to begin her defence case on Thursday.
But before she took the stand, Judge John Saunders instructed the jury to formally acquit the 45-year-old of one charge of misconduct in public office.
Brooks was accused of sanctioning a payment of $US4000 ($A4456) to a public official for a picture of Prince William, dressed as a bikini-clad Bond girl at a party at army training school Sandhurst.
The image was never published but led to a story in the Sun, the Murdoch-owned daily that Brooks edited between 2003 and 2006, with the headline "Willy in a Bikini" together with a mocked-up picture of the prince in a green swimsuit.
"I have decided that there is no case for Ms Brooks to answer on count four," the judge said. "That is the charge relating to a picture of Prince William in a bikini."
Brooks smiled as the foreman of the jury recorded a not-guilty verdict.
Her four other charges include one count of conspiring to hack phones, two counts of conspiring to pervert the course of justice by concealing evidence, and one count of conspiring to commit misconduct in public office - namely, paying an official for information.
Six other defendants are on trial, including her deputy at the News of the World and successor as editor, Andy Coulson, who is accused of phone hacking and paying officials for stories.