The trial of a senior counter-terrorism detective accused of passing information to the News of the World is due to begin today.
Det Chief Insp April Casburn, 53, is accused of offering the now-defunct tabloid information about Operation Varec, the investigation into whether Scotland Yard's inquiry into phone hacking should be reopened.
She is due to appear at Southwark Crown Court today on one count of misconduct in public office, which she denies.
The trial is expected to take a week.
Casburn, from Hatfield Peverel, Essex, is also facing a separate charge under the Official Secrets Act that can only be dealt with by magistrates.
It is alleged that she had secret documents at her home without permission to keep them there.