In a joint statement released last October, the group said they had become aware of “compelling and highly distressing evidence” that they had fallen victim to “abhorrent criminal activity and gross breaches of privacy”.

They alleged that ANL “habitually utilised unlawful information gathering as part of the modus operandi of preparing stories” during the relevant period.

All seven claimants are represented by barrister David Sherborne, who defended the use of financial documents supplied by Associated to the Leveson inquiry as the basis for the claim.

The Duke’s claim concerns a period “from at least as early as 2001” until “2013 and beyond”.

Flying visit

He made an unannounced appearance at the High Court in March, flying to London from California.

Sir Elton, Mr Furnish, Ms Frost and Baroness Lawrence joined him for part of the preliminary hearing.

Harry said in his witness statement that he was “horrified” Associated had so far avoided proper scrutiny “through its cover-up” and had behaved as if it was above the law, portraying itself as “a beacon of truth and integrity.”

He warned that if an influential newspaper company could successfully evade justice “the whole country is doomed” as he railed against the “unchecked power, influence and criminality” of the newspaper group.

He accused the Royal Family of trying to keep from him the full extent of phone hacking at the now defunct News of the World and claimed that they did not want to pursue litigation because it “could open a can of worms.”

Harry said the publisher’s behaviour amounted to “a major betrayal” given promises made by the media to improve its conduct following the death of his mother, Diana, Princess of Wales, in 1997.

‘Real prospect’

In his 95-page-judgment, Mr Justice Nicklin said: “In my judgment, each claimant has a real prospect of demonstrating that Associated, or those for whom Associated is responsible, concealed from him/her the relevant facts upon which a worthwhile claim of unlawful information gathering could have been advanced.

“Whilst it is common ground that the publication of any unlawful articles was not concealed, these were, on the claimants’ case, only the tip of the iceberg.

“What was deliberately hidden from the claimants – if they are correct in their allegations – were the underlying unlawful acts that are alleged to have been used to obtain information for subsequent publication.”

The judgment added: “Fair resolution of any limitation defence…must await trial.”

Associated strenuously denies the allegations, which it has described as “preposterous smears” and a “pre-planned and orchestrated attempt to drag the Mail titles into the phone hacking scandal”.