News of the World royal editor Clive Goodman was today jailed for four months at the Old Bailey for plotting to hack into Royal aides' telephone messages.
Judge Mr Justice Gross told him: "This was low conduct, reprehensible in the extreme.
"This case is not about press freedom. It is about grave, inexcusable and illegal invasion of privacy.
"The targets were members of the Royal Family. The Royal Family holds a unique position in the life of this country. It is grave indeed."
Mr Perry said the prosecution case was that over approximately eight months between November 2005 and June last year, the defendants gained access to voicemail messages left on the mobile phones of three members of the royal household.
He added: "The purpose of gaining access was to gain confidential information with a view to it being published in the News of the World newspaper."
He said Mulcaire, who has also pleaded guilty to five other charges involving other well-known figures, had accessed other voicemail messages between February and June last year.
Mulcaire, a former footballer, admitted intercepting voicemail messages for publicist Max Clifford, footballer Sol Campbell's agent Skylet Andrew, chairman of the Professional Footballers Association Gordon Taylor, MP Simon Hughes and supermodel Elle Macpherson.
"The inference to be drawn is that he was also motivated by profit, seeking confidential information with a view to selling it to the press," said Mr Perry.
He said the two men had used mobile numbers and secret codes used by mobile phone network operators to break into the voicemails.
Lawyers on behalf of Goodman and Mulcaire apologised to the Prince of Wales, Princes William and Harry and their household for a gross invasion of their privacy at a previous hearing.
The conspiracy charge relates to intercepted voicemail messages on the telephones of the Prince of Wales's aide Helen Asprey, Jamie Lowther-Pinkerton, the ex-SAS officer who is private secretary to Princes William and Harry, and Charles's communications secretary Paddy Harverson.
The court heard the two defendants made a total of 609 calls to the mobile phones of Ms Asprey, Mr Lowther-Pinkerton and Mr Harverson.
Of those, 487 were made by Mr Goodman and 122 made by Mr Mulcaire.
Mr Perry said the calls ranged from a few seconds to several minutes and it toook just nine seconds to access messages in the mobile phones.
"The defendants in the short calls were fishing in the voicemail boxes to see whether there might be information of interest to them," he said.
"The prosecution in this case is that the defendants acessed the voicemail boxes of the telephones remotely, so in other words they used their own telephones and dialled the retrieval numbers and entered the pin codes in order to gain access to the mail boxes.
"They used the personal retrieval numbers and pin codes for their own commercial purpose - Mr Mulcaire for purely financial benefit and Mr Goodman to provide the basis for stories to be published in the News of the World."
Mr Perry said they used a combination of mobile and landline telephones to hack into the voicemail boxes, including Mr Goodman's office at News International in Wapping, east London, and his home in Putney, south west London.
Mr Perry said Mr Harverson first became aware of a problem in December 2005 when he found that messages he had not listened to were shown as old messages.
He said Mr Harverson, the communications secretary for the Prince of Wales and Duchess of Cornwall, regularly received messages regarding future events involving the Royal Family.
Mr Perry continued: "Analysis of the telephone records demonstrates that, having dialled retrieval numbers, the defendants listened to the messages in the voicemail."
Mulcaire ran a company called Nine Consultancy on an industrial estate in Sutton, Surrey, and was listed as its director of operations.
Ironically, it had offered a service protecting clients from media intrusion, said Mr Perry.
"The contents of the documents found at the time might be thought to be both cynical and ironic as he was conducting an operation to intrude into the personal life of individuals," he said.
Mulcaire's notebooks had contained details of the tapping scheme, together with numbers and codes.
He had access to network passwords and was recorded posing as a credit controller to trick telephone companies to switch Pin codes to default numbers, therefore enabling access to voicemails.
Mr Perry said Mulcaire had signed a contract with the News of The World worth £104,988 annually for "research and information services".
In the contract - dated from July 1, 2005 to June 30, 2006 - he promised to work exclusively for the newspaper.
In addition, Mulcaire was given "cash payments" from the paper - through Goodman - amounting to £12,300 between November 9, 2005 and August 7, 2006.
Mr Perry said: "A claim for expenses was made by Mr Goodman. He was in effect paying cash to Mr Mulcaire, claiming that on expenses through the company."
Internal documents released by News International showed reference to "Research/Alexander/Goodman" - Alexander was the name used by Mulcaire.
Mr Perry said cash in instalments of £500 was given to Mulcaire with reference names such as "Fergie, Harry, Chelsey, Harry, Wills".
The court heard how Mulcaire sent Goodman text messages with the private Pin codes for the various phones "to enable Mr Goodman himself to gain access to the voicemail boxes".
A search by police of Goodman's office at News International revealed a document revealing Mr Harverson's voicemail retrieval number and his Pin code.
Both men were arrested on August 8 last year - Goodman at home in Putney and taken to Charing Cross police station, Mulcaire at home in Cheam and taken to Belgravia police station.
Neither man made any comment and both were charged the following day with conspiracy to intercept communications and number of substantive charges.