I have learned that News of the World e-mails uncovered by News International in 2007 contained evidence that the Sunday newspaper was paying a Royal Protection Officer for the contact details of senior members of the royal family, their friends and their relations.
According to a source, the e-mails include requests by a reporter for sums of about £1,000 to pay police officers in the royal protection branch for the information. The phone details could have been used to hack phones of the royal family.
"There was clear evidence from the e-mails that the security of the royal family was being put at risk," the source said. "I was profoundly shocked when I saw them."
The source added that the e-mails were unambiguous signs of criminal activity at the News of the World.
"It is quite astonishing that these emails were not handed to the police for investigation when they were first found in 2007", he said.
The e-mails were not passed to the Metropolitan police until 20 June this year, when they were re-obtained - from the offices of the solicitors Harbottle and Lewis - by a recently appointed new team of News International executives.
James Murdoch, News International's chairman, has said he was not in the picture about the full extent of wrongdoing at the News of the World until recently.
You can read more about these e-mails in my blog of yesterday. And I will publish some additional details in a bit.
Update, 13:55: I can now disclose more detail about the extraordinary e-mails that appear to show royal protection officers were selling confidential information to the News of the World.
In one of the dynamite e-mails, Clive Goodman - the paper's disgraced former royal editor - was requesting cash from the newspaper's editor, Andy Coulson, to buy a confidential directory of the Royal Family's landline telephone numbers, and all the phone numbers - including mobiles - of the household staff.
The relevant e-mail implies that a police officer in royal protection had stolen the directory, which is known as the Green Book, and wanted £1000 for it.
The Green Book contains, for example, the home numbers of Princess Anne, Prince Edward and so on. It provides more complete contact details of officials working for all the Royal Family.
The directory is stamped "secure" on the cover. When members of the royal household receive a copy they have to sign for it. And it is supposed to be locked away when not in use.
The implication of the e-mails is that the News of the World had bought the Green Book on at least one previous occasion.
The e-mails also suggest that the News of the World had police contacts in a number of royal palaces, and had bought information from several of them.