Police raided the home of a retired Special Branch detective who acted as a whistleblower on the failure of authorities to investigate media dirty tricks, just days before he is to give evidence as a witness to Lord Leveson's inquiry.
Alec Owens, formerly of Merseyside Police, was the lead investigator for the Information Commissioner's "Operation Motorman" inquiry, which uncovered the vast scale on which the media used private detectives to obtain private information, including criminal records and vehicle registrations.
But he is a critic of the ICO's decision not to interview any of the hundreds of journalists named in the 17,000 transactions listed in files seized from Hampshire private detective Steve Whittamore in 2003. No journalist was charged in Operation Motorman.
Mr Owens contacted Lord Justice Leveson about his concerns over the way the matter was handled and is due to give evidence in person to the public inquiry on media standards on 30 November. Richard Thomas, the Information Commissioner at the time of Operation Motorman, will appear before the inquiry the next day.
At 7.25am yesterday, two police officers from Wilmslow, Cheshire, armed with with a search warrant, knocked on Mr Owens' door. They demanded documents and electronic files and asked him to come to a police station to be questioned under caution.
Cheshire Police said it had acted "following information received". A spokeswoman added: "The warrant relates to an investigation into allegations concerning breaches of the Data Protection Act 1998."
Mr Owens agreed to hand over his copy of the Operation Motorman computer file but declined to provide the statement he has prepared for Lord Justice Leveson's inquiry. He was asked to attend an interview on Monday and bring the statement with him.
Mr Owens, who has notified Lord Justice Leveson's office of the development, said he believed the raid was connected to his inquiry evidence. "They have come on a fishing expedition to find out what I'm going to say," he said. "But I have told them that statement is for Lord Leveson's eyes only at this stage."
He has already provided a statement and a copy of the Motorman disk to Strathclyde Police, which is investigating media dirty tricks in Scotland. "This is vindictiveness," he said of yesterday's raid. "They want to know what hard evidence I have got and what I am going to say to the Leveson Inquiry." Mr Owens maintains that there are errors that need to be corrected in official reports on Operation Motorman.
In September, The Independent revealed that the Operation Motorman files included previously unpublished details of how tabloid newspapers used private detectives to target figures such as the Duchess of Cambridge and Chelsea Clinton when they were students.
Investigators were also used to target the private information of families of murder victims such as Sarah Payne and Holly Wells.