Prince Harry was ordered on Thursday to carry other wider searches for emails, text messages and other material that might be relevant in his lawsuit against Rupert Murdoch's UK newspaper arm, amid concern some evidence had been destroyed.
The Duke of Sussex, 39, the younger son of the UK's King Charles, and more than 40 others are suing News Group Newspapers (NGN) over accusations of unlawful activities by journalists and private investigators, for The Sun and the now-defunct News of the World from the mid-1990s to the mid-2010s.
A trial focusing on some of those claims, possibly including Prince Harry's, is due to begin at the High Court in London in January.
NGN, which is contesting the claims, has paid out hundreds of millions of pounds to victims of phone-hacking by News of the World and settled more than 1300 lawsuits, but has always rejected allegations of any wrongdoing by staff at The Sun.
Ahead of the trial, NGN's legal team sought an order to force Prince Harry to disclose any relevant information that he might possess, or that might be held by his former lawyers or the royal household, which would be relevant to what he knew about alleged unlawful behaviour before the end of 2013.
If Prince Harry, the Duke of Sussex, knew he had a potential claim against NGN before that date, then the case could be dismissed on the grounds it was filed too late.
"I have real concerns that the issue of disclosure related to the 'knowledge issue' has not been dealt with adequately by the claimants' solicitors," said Judge Timothy Fancourt, adding so far they had produced only five documents assessed to be relevant.
He also said it was not appropriate most of the searching and selection of relevant documents appeared to have been done by the duke himself until very recently.
'Kicking and screaming'
Anthony Hudson, NGN's lawyer, had earlier told the court that Harry had been creating an "obstacle course" on the issue, and the disclosure of other possibly relevant emails had also been highly unsatisfactory.
"We have had to drag those out of the claimant kicking and screaming," he said.
Fancourt said there was "troubling evidence" a large number of potentially relevant documents and messages over the messaging app Signal between Prince Harry and JR Moehringer, the ghostwriter of his hugely successful memoir Spare, had all been destroyed.
"The position is not transparently clear about what happened," the judge said, citing how Moehringer later wrote they had been "texting round the clock" and it was likely they would have discussed matters relating to unlawful behaviour by newspapers.
Prince Harry's lawyer David Sherborne responded by accusing Hudson of using language to "get a headline" and said NGN's legal team were guilty of simply carrying out a fishing expedition.
He said the suggestion Prince Harry was withholding or destroying material was the "height of hypocrisy", saying NGN had deliberately deleted millions of emails as part of a way to hide incriminating evidence.
However, Fancourt ruled a wider search was required of Prince Harry's laptop, text and WhatsApp messages, to look at exchanges from 2005 until early 2023, and an attempt should be made to retrieve the Signal exchanges. The duke also needed to produce a witness statement to explain the Moehringer exchange.
He said letters should be also sent to the royal household and its lawyers asking for any hard copies or electronic documents they held relating to Prince Harry's communications should be returned to the prince so that they too could be examined.
The judge also ordered Prince Harry to make an interim payment of 60,000 pounds (NZ$125,000) to NGN towards its costs for the hearing.
