Records seized from investigator Steve Whittamore in 2003 contained a "veritable treasure trove" of information about how newspapers ordered searches on everything from addresses to criminal records, the hearing was told.
The paperwork includes references to investigations into members of a UK national sports team and a "B&B sex party".
Whittamore was asked to do an address search for Grant and Hurley in south London and a vehicle registration mark (VRM) check relating to the Love Actually star, the press standards inquiry heard.
Alec Owens, senior investigating officer for the Information Commissioner's Office (ICO) from 1999 until 2005, recalled: "We went to see Mr Grant at his offices because a VRM comes up against his name.
"As it turned out he couldn't recall this and possibly thought he may have been in a friend's car or talking to somebody standing by that car."
One newspaper paid £800 in 2002 for the June 2001 phone bill of an unnamed sports star from a national side, the inquiry was told.
Whittamore's Hampshire home was raided in March 2003 as part of a major ICO investigation into the illegal purchase of confidential information called Operation Motorman.
The private detective was convicted in 2005 of illegally accessing data and passing it to journalists.
Robert Jay QC, counsel for the inquiry, said there was a "veritable treasure trove" of information in Whittamore's files.
Inquiry chairman Lord Justice Leveson added: "Mr Whittamore had collected together a vast amount of personal data.
"The documents identify the names of titles, specify journalists at the titles apparently or inferentially making the requests.
"It identifies the names of people from a wide range of public life and in the public eye, and provides addresses, telephone numbers, mobile telephone numbers and charging details for that information."
The records show that Whittamore charged £17.50 for an "occupancy search" to discover who lived at a particular address, £30 for an "area search" to find out where a person lived, and about £75 for an ex-directory telephone number search.
Newspapers paid £75 for getting the address linked to a mobile number and £150-200 for a vehicle registration search.
Whittamore would write "occupancy" on paperwork that he sent to his accountant for tax purposes when in fact it related to ex-directory phone number searches, while invoices sent to newspapers often just read "confidential inquiries", the hearing was told.
Mr Owens said: "In the main it was just 'confidential inquiries'. He (Whittamore) wouldn't tell us and we never got the opportunity to ask any members of the press what they might have been."
Singer Charlotte Church told the inquiry last week that she was contacted by police when she was 19 over Operation Motorman.
She said in a witness statement: "I was shown an enormous book which included transcripts of telephone calls as well as addresses, car registration details, and information from criminal records.
"There was a huge amount of information, and I am not sure what became of it."
The inquiry has heard that former Information Commissioner Richard Thomas did not pursue investigations against any journalists, despite the wealth of evidence unearthed.
Today it emerged that Mr Thomas had also been warned that even editors could be implicated.
Counsel giving him written advice on whether there were grounds for bringing legal action said: "Having regard to the sustained and serious nature of the journalistic involvement in the overall picture, there could be little doubt that many, perhaps all, of the journalists committed an offence.
"It seems to me that several editors must have been well aware of what their staff were up to and therefore party to it."
But counsel went on to note that this was apparently "the first occasion on which the scale of the problem has come to light".
And they suggested that "it may not be unreasonable to give the Press Complaints Commission the chance to put their house in order".
Mr Owens told the inquiry last week that the former deputy head of the ICO said the media groups were also "too big" for the office to take on.
Told of the paper trail apparently connecting newspapers with the illegal purchase of confidential information, Francis Aldhouse was alleged to have said with a look of horror on his face: "We can't take them on, they're too big for us."
But, giving evidence today, Mr Aldhouse denied he had ever said any such thing.
That was "simply not my view", he said, and "certainly not the sort of language I would use".
And he insisted he did not fear the media.
"Not only do I have no recollection of saying that, it's simply the sort of thing I would not say and does not reflect my views or indeed my previous practice of dealing with the media," he said.
He also claimed he had no recollection of having a meeting with Mr Thomas and Mr Owens at which the latter explained what material he had found.
"I can't recall such a meeting," he said. "If there was a meeting, it would have been a very casual one and a very short one and certainly not a scope for a full briefing."
He also denied seeing the contents of Whittamore's notebooks.
Asked whether he had discussions with Mr Thomas about what policy they would adopt on how the issue should be investigated and pursued, he said: "I do recall that Richard Thomas decided he wanted to pursue the route of going to the Press Complaints Commission and writing to (then chairman) Sir Christopher Meyer.
"I think that was Mr Thomas's decision, rather than the result of some discussion."
He described the Commissioner as a "one-man band", adding: "If the Commissioner decides to take a route, so be it."
Had he seen in 2003 the information laid out as it had been today, his view would have been that "we really ought to find a way of pursuing this", he said.
He was "not quite sure whether we could have put together the resource to handle such an investigation", he said.
But he added: "I do think there was a case for taking the involvement of journalists and newspapers further."
However, there would have been practical difficulties in pursuing newspapers as part of Operation Motorman, Mr Aldhouse went on.
He told the inquiry: "Why should a journalist respond to our request for interview?
"The commissioner has no power of arrest, has no power to compel people to speak to him.
"We would be seeking to interview journalists presumably as prospective defendants to a criminal action.
"They would have to be cautioned. A well-advised journalist would simply say nothing."
Newspapers may also have been able to mount a public interest defence, Mr Aldhouse suggested.
Referring to some of the people whose "friends and family" phone numbers were obtained by Whittamore, Lord Justice Leveson observed: "If you were going to say there's a public interest in looking at those, you might as well then say that data protection doesn't run to journalists."
Mr Aldhouse replied: "There are those who think that the legislation was constructed to achieve just what you are saying."
Author Peter Burden told the inquiry
he had uncovered evidence that reporters and photographers at the News of the World fabricated stories and pictures for decades before the phone hacking scandal broke.
He said: "The idea of simply getting the story by any means, whether it was by 'stunting' (faking) photos or entrapping people, was embedded in the culture, the ethos of the newspaper by then, which would seem to set the right sort of background for people to be prepared to take subsequent risks on things like phone hacking."
Mr Burden, whose books include News of the World? Fake Sheikhs & Royal Trappings, supported the introduction of a French-style privacy law in Britain.
He said: "I don't see that there's any problem in saying to the press, 'you can't transgress this far into a person's private life unless you are uncovering a crime or deep corruption'."
Prime Minister David Cameron set up the Leveson Inquiry
in July in response to revelations that the News of the World commissioned a private detective to hack murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry,
sitting at the Royal Courts of Justice in London, is looking at the culture, practices and ethics of the press in general and is due to produce a report by next September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police,
and any prosecutions have been concluded.
PA
