Prince Harry and a group of six other high-profile figures have been ordered to make an initial payment of £9.54m in legal costs to the Daily Mail's publisher after they lost their High Court privacy case.
The seven claimants, also including Sir Elton John and Liz Hurley, must pay the initial figure by 28 August - and could potentially pay up to £25m more after that in a victory for Associated Newspapers Limited (ANL).
The group had sued ANL over allegations of unlawful information-gathering, which the publisher had strenuously denied.
On 7 July, Judge Mr Justice Nicklin dismissed the claims and said the public figures had failed to prove the allegations.
The judge ruled that he was making an exceptional order to force the Duke of Sussex and others to pay up to £34.5m in costs incurred by the newspaper group because of the way the case had been brought - including unsupportable claims that top executives from the group had lied to the Leveson public inquiry.
Prince Harry and the other six claimants have until 2 October to attempt to launch an appeal.
Those other claimants are Sir Elton John and his husband David Furnish, Sir Simon Hughes, Sadie Frost, Liz Hurley, and Baroness Doreen Lawrence.
The judge also ruled that ANL's costs should be determined on an indemnity basis, which is more favourable to the publisher in terms of the amount it can recover, aside from where orders had already been made.
The claimants had insurance to cover up to £16.2m of Association Newspapers' costs in the event of losing the case - but Friday's ruling means the newspaper group could now try to recover up to the £34.5m that it said it had to spend to defend itself. This means the Duke and others could face a bill of some £18m.
Justice Nicklin described the potential £34m payment to ANL as "excessive", suggesting the costs for the group will not rise to that extent.
The judge said: "I regard a claim for costs in excess of £34 million as, on its face, excessive and as giving rise to real concerns as to whether all of the costs now claimed by Associated were reasonably incurred and are reasonable in amount."
But he added he had "decided not to impose a ceiling on Associated's recoverable costs", as it would "be too broad brushed, would risk unfairness, and would be vulnerable to the charge that it was arbitrary".
He added it was "striking" that "not a single allegation of serious wrongdoing was voluntarily withdrawn" by the group of seven claimants.
He said: "That matters. Serious allegations of criminality or grave impropriety cannot properly be left hanging over individuals in that way.
"If a party no longer advances such an allegation, or no longer has a proper evidential basis for advancing it, the allegation should be withdrawn clearly and in terms.
"The claimants' failure to do so was not ordinary forensic judgment. It was not a proper or disciplined way to deal with serious allegations. It was unreasonable to a high degree."
In a statement released on Friday, the publisher called the ruling " a devastating critique of an attempt to destroy a newspaper and the reputations of its journalists, editors and executives".
Friday's decision comes just days after the Duke and Duchess announced their plan to return to the UK, with their children Prince Archie, seven, and Princess Lilibet, five, enrolled to start school in September.
During the trial, dozens of people gave evidence including Prince Harry and the other claimants. The Duke of Sussex flew in from the US to attend court in person.
Many current and former Associated Newspapers journalists and executives gave evidence denying illegal activity.
Sir Simon Hughes told the BBC he was "disappointed" by the judgement.
"I am now taking the time necessary to consider both the substantive and the costs judgment and whether to pursue appeals against decisions in either judgment or both," he added.
In a joint statement following the judge's ruling last month, Prince Harry and Baroness Doreen Lawrence, another claimant and peer whose son Stephen was murdered in 1993, said: "We came to Court seeking justice and accountability. But we have received neither."
"It is a complete and obvious whitewash, but sadly not altogether unexpected", the pair added.
ANL had asked for more than £9.9 million as an interim payment ahead of future hearings to decide its legal costs in depth.
However, lawyers for the claimants said the interim payment should be just over £7.9 million.
Mr Justice Nicklin previously said the claimants would need to pay the interim payment on 28 August.
Source: BBC
-Agencies
