Former chief reporter Thurlbeck, who was originally held last April during the phone hacking scandal, took himself to a central London police station earlier today (Wednesday) at 4pm.
Thurlbeck is being questioned by detectives from Operation Weeting, the investigation into phone hacking at the News of the World.
"A 51-year-old man was arrested by appointment at a central London police station at approximately 4pm today by officers from Operation Weeting," Scotland Yard said in a statement
"He was arrested on suspicion of intimidation of a witness and encouraging or assisting an offence."
Rebekah Brooks and husband Charlie were yesterday given police bail on "suspicion of conspiracy to pervert the course of justice", relating to the same investigation.