LONDON (AP) — A yellow school bus with a banner depicting the face of Britain’s Prince Andrew drove past Buckingham Palace on Friday, urging him to testify in the investigation of the late sex offender Jeffrey Epstein.

The stunt organized by American lawyer Gloria Allred sought to pressure Queen Elizabeth II’s son to reveal what he might know about the disgraced financier. Allred represents some of Epstein’s victims and has demanded that Andrew cooperates.

The message, featuring pictures of Andrew, said: “If you see this man please ask him to call the FBI to answer their questions.”

Andrew has stepped back from royal duties following a catastrophic BBC interview in which he categorically denied having sex with a teenager who says she was trafficked by Epstein. Britain’s newspapers and social media commentators slammed the royal for defending his friendship with Epstein and for failing to show empathy for the convicted sex-offender’s victims.

U.S. Attorney Geoffrey Berman told reporters in January that Andrew has provided “zero cooperation” to the FBI and U.S. prosecutors seeking to speak with him about Epstein.

The statement by Berman, the top federal prosecutor in Manhattan, was the first official confirmation that the leading U.S. law enforcement agency had sought — and failed — to obtain evidence from Andrew, third child of the monarch, despite his pledge to cooperate with legitimate law enforcement agencies.

Andrew was reported to be “angry and bewildered” at the comments by American authorities, with the Telegraph quoting a source as saying: “The duke is more than happy to talk to the FBI but he hasn’t been approached by them yet.”

The American prosecutors have since stood by their statements.

The FBI declined to comment.