The 66-year-old prince, who is the younger brother of King Charles, was arrested in February at his Norfolk residence after the release of millions of documents by the U.S. Department of Justice linked to the late American sex offender Jeffrey Epstein.

British police on Friday said investigations into Andrew Mountbatten-Windsor over alleged misconduct in public office would be lengthy and highly complex following his arrest earlier this year, according to Reuters.

The 66-year-old prince, who is the younger brother of King Charles, was arrested in February at his Norfolk residence after the release of millions of documents by the U.S. Department of Justice linked to the late American sex offender Jeffrey Epstein.

Mountbatten-Windsor was later questioned under caution for several hours by detectives in what has become one of the most significant criminal investigations involving a senior British royal in modern history.

Thames Valley Police said part of the inquiry concerns his role as Britain’s special representative for trade and investment between 2001 and 2011 after emails released by U.S. authorities allegedly suggested sensitive information may have been shared with Epstein.