The Charles versus Associated Newspapers court hearing shone a light on how The Mail on Sunday returned the journals to the "source" only for the paper to go ahead and publish them a month later.
The court heard that Charles has kept hand-written journals for 30 years and that on his return from trips abroad, he often circulates photocopies to family, close friends and advisors in envelopes marked "private and confidential".
According to the prince’s principal private secretary, Sir Michael Peat, Charles has no intention of ever publishing the journals, but edited extracts may appear after his death.
The High Court judgment states that former royal secretary Sarah Goodall was almost certainly the source of the journal leak.
MoS editor Peter Wright would only reveal that the journals came from an "unnamed source" who had "legitimate access" to them.
The court heard that it was MoS diary editor Katie Nicholl who was originally approached by an "intermediary" offering to sell the journals in May 2005, and was later given typed copies of them.
There was a considerable delay as the MoS established the journals were genuine and then, on 14 October, Nicholl received a call from Goodall saying that the journal copies were hers and she wanted them back.
Later that day, MoS managing editor John Wellington met Goodall and, according to the judgment, gave her the "benefit of the doubt" that she was the source and gave her a copy of the set of journals.
According to the MoS its unnamed intermediary later denied that Goodall was the source.
On Saturday, 5 November, Nicholl read out excerpts from the Hong Kong journal to Prince Charles’s press office.
Lawyers became involved and the MoS gave an undertaking not to publish them the next day.
Despite a letter threatening legal action, the MoS pressed on and published the journals on 13 November.