A retired Scotland Yard officer was arrested today by detectives investigating inappropriate payments from journalists.
The 57-year-old - who served on the force's command that defends Britain against terror - is being questioned on suspicion of misconduct in a public office, relating to the phone-hacking scandal.
His home is being searched by Operation Elveden officers after a swoop on the property at 6.30am.
The 27th arrest under Elveden comes after information was provided to police by News Corporation's management standards committee (MSC).
The latest suspect, from Surrey, worked as part of the force's Specialist Operations command, which has a host of security responsibilities from providing armed protection services for ministers and the Royal Family to counter-terrorism intelligence gathering.
The inquiry into allegations of inappropriate payments to police and public officials runs alongside the force's Operation Weeting investigation into mobile phone interceptions.
A force statement said: "The 57-year-old man was arrested at his home address.
"He previously served in the MPS Specialist Operations command, based in central London, and retired several years ago.
"He is currently being questioned at a south west London police station and his home address is being searched."
The force added that the arrest "is not about seeking journalists to reveal confidential sources in relation to information that has been obtained legitimately".
The arrest comes a fortnight after The Sun's royal editor, Duncan Larcombe, was arrested along with a 42-year-old former member of the Armed Forces and a 38-year-old woman as part of the same inquiry.
The MSC was set up in the wake of the phone-hacking scandal that led to the closure of the News of the World last July.
It is carrying out internal investigations relating to Rupert Murdoch's remaining UK papers - The Sun, The Times and The Sunday Times - and is working closely with the detectives investigating alleged phone hacking and corrupt payments.
The Crown Prosecution Service confirmed last month that it has received the first set of files from police relating to the inquiries.
PA