A 60-year-old man, understood to be former News of the World head of legal Tom Crone, has been arrested by Metropolitan police detectives investigating phone hacking.
Crone was arrested at his home address in south-west London on Thursday morning on suspicion of conspiracy to intercept communications.
It is understood that the arrest followed the passing of information from News International's management and standards committee and Crone had no prior notice that the police were to make the arrest.
He is the 25th person arrested as part of the Operation Weeting investigation into phone hacking.
The Met said the man was being questioned at a south London police station on Thursday morning.
He is the first to be arrested under Operation Weeting since the Crown Prosecution Service brought phone-hacking charges against several former News of the World journalists, including ex-chief executive Rebekah Brooks and former editor Andy Coulson, earlier this month.
The force said in a statement: "Officers from Operation Weeting, the MPS inquiry into the hacking of telephone voicemail boxes, arrested a man in south-west London this morning, Thursday 30 August.
"The 60-year-old man was arrested at his home address at approximately 06.45 hrs this morning on suspicion of conspiring to intercept communications contrary to section 1 of the Criminal Law Act 1977. He is being interviewed at a south London police station."
Crone was the legal manager of News International's tabloids, the Sun and News of the World, for 26 years until July 2011.
He worked alongside a succession of News of the World editors – including Piers Morgan, Brooks and Coulson – and was privy to some of the paper's most memorable front-page splashes.
Crone clashed with his former News International bosses earlier this year over evidence given to both the Leveson inquiry into press standards and a House of Commons committee on phone hacking.
He accused James Murdoch, former News International chairman, of giving false information over the so-called "for Neville" email in 2008, which indicated that hacking went further than one rogue reporter at the title. Murdoch denies this claim.