A former Scotland Yard detective who complained of being spied on by the News of the World during a major murder inquiry has been arrested over illegal leaks to a journalist.
The 52-year-old - named by sources as Detective Chief Superintendent Dave Cook - was questioned on suspicion of misconduct in public office after being detained at his Berkshire home yesterday.
Officers from the Independent Police Complaints Commission questioned him on the basis of evidence from the Scotland Yard team investigating corruption surrounding the phone-hacking investigation.
Cook's name was previously linked to the phone-hacking scandal when relatives of murdered private investigator Daniel Morgan said the Sunday tabloid had followed the officer during his inquiries into the killing.
Cook claimed he was watched from a surveillance van outside his home and followed driving his children to school, according to Mr Morgan's brother Alastair.
The surveillance was said to have taken place months after missing schoolgirl Milly Dowler's mobile phone was hacked in 2002.
The former officer was bailed until March yesterday evening after having been questioned by IPCC investigators at a Thames Valley police station.
Nine suspects have now been arrested as part of Operation Elveden, which was launched after officers were handed documents suggesting News International journalists had made payments to officers.
Sir Paul Stephenson, the then Met commissioner, said in July that evidence from the publisher suggested a small number of officers were involved.
Last month, a 52-year-old woman, understood to be a member of the Metropolitan Police's specialist operations branch, was arrested on suspicion of receiving illegal payments.
Others questioned as part of the inquiry include former News International chief executive Rebekah Brooks, ex-Downing Street communications chief Andy Coulson, former News of the World managing editor Stuart Kuttner, the paper's former royal editor Clive Goodman, and a 63-year-old man whose identity has not been disclosed.
Cook was alleged to have been placed under surveillance after appearing on the BBC's Crimewatch programme to make a fresh appeal about the murder of Mr Morgan, who was found dead in a pub car park in 1987.
Alastair Morgan said in July last year: "I learned about the surveillance and then I learned that it was the News of the World carrying out the surveillance.
"Dave told me that he was taking his dog out for a walk one evening and he noticed a van parked in an odd location.
"Obviously it aroused his suspicions. The following morning, he noticed that he was being followed."
The paper was said to have claimed it was investigating whether or not Cook was having an affair with Jacqui Hames, a co-presenter on Crimewatch, to whom he was in fact married at the time.
No-one has been brought to justice over the murder. A trial collapsed, after five police inquiries.
Detective Chief Superintendent Hamish Campbell apologised to Mr Morgan's family in March, admitting that police corruption was a "debilitating factor" in the case.