The Duke of Sussex is continuing his lawsuit against the publisher of the Sun over allegations of unlawful information gathering as a judge ruled he can use further emails between newspaper executives and members of the palace staff in his legal claim.

Prince Harry “is one of two claimants whose claims are still live” against Rupert Murdoch’s News Group Newspapers (NGN), his barrister David Sherborne said, with the other being the former deputy Labour leader Tom Watson. The court was told 39 cases had been settled since a previous hearing in July.

The two cases are expected to go to trial in January. Harry alleges he was targeted by journalists and private investigators working for NGN, which also published the now defunct News of the World. NGN has denied unlawful activity took place at the Sun.

Lord Watson attended the hearing but Harry was not present.

Lawyers for the duke sought access to “highly relevant emails” sent between five royal household staff and five senior NGN employees. They included Rebekah Brooks, the chief executive of News UK from September 2015, Robert Thomson, the chief executive of News Corp from 2013, and Mike Darcey, the chief executive of News UK until September 2015, as well as Sir Christopher Geidt, the former private secretary to Queen Elizabeth II, his successor Sir Edward Young, and Sally Osman, a former head of royal communications.

The judge ruled that a limited number of the emails requested by the duke could be disclosed, saying that while there was a “degree of speculation whether any of the documents sought are going to assist the claimant’s case”, there was “sufficient justification” for some of the emails to be provided, and that there was a credible case for saying a full picture was necessary in the interest of justice.

Harry has previously claimed he could not bring his case earlier because there was a “secret agreement” to delay “resolution and recompense” between NGN and the palace until the conclusion of civil cases against the publisher, a claim NGN has previously dismissed as “Alice in Wonderland stuff”

Sherborne said previous emails submitted to the court by NGN were incomplete and had been “cherrypicked”. It was “not fanciful” that further emails contained discussions from which “inferences can be drawn” that could go to the issue of liability and “knowledge”.

Previously disclosed emails suggested there were discussions about the NGN paying compensation and apologising to members of the royal family, Sherborne said. Further email disclosure could also show “the extent to which a brake was applied by the palace” on Harry’s claim, and the “information that was or was not passed on to the claimant about NGN’s position,” he said in written argument.

One, in July 2017, by Osman referenced a meeting with her, Thomson and Geidt “to discuss a conversation over ‘resolution and recompense’ which has ‘the Queen’s full authority and knowledge and the scale and effect of hacking and surveillance,’” claimed Sherborne in written argument.

In another, in 2018, Harry asked the royal family’s solicitors for an update and received the response: “[T]here are certain issues about agreeing the date of the publication of the apology,” and that NGN was “bidding against themselves” and “there is a rough sliding scale however we are off the end of it”. Harry was told: “The ball is with Murdoch.”

Anthony Hudson KC, for NGN, said it was “clearly a speculative fishing exercise” and any emails had to be viewed in the context of 2005, when allegations were made against News of the World culminating in its royal editor and a private investigator being convicted of phone hacking.

Hudson told the judge: “The documents sought are not relevant to the pleaded issues in the Duke of Sussex’s case, are not necessary to ensure a fair trial will take place and are not likely to make a real difference to the prospect of settlement of the claim; and, moreover, the proposed searches would be disproportionate and would not save costs.”

The high court has previously ruled that voicemail interception claims cannot be part of the duke’s case at trial.

In Friday’s ruling, the judge quoted from documents recently filed by Harry’s lawyers, which said Harry will argue at trial that his father “acted to discourage and stymie him” from suing NGN.

The trial is expected to last between six and eight weeks.

Harry’s lawyers have previously said the late Queen Elizabeth authorised her staff to seek a resolution. Harry’s legal team have claimed Prince William settled a case against NGN in 2020.

Many others have settled their claims in recent years including Hugh Grant, Sienna Miller, Paul Gascoigne, Catherine Tate and Melanie Chisholm.

A spokesperson for NGN said: “In 2011 an apology was published by NGN to victims of voicemail interception by the News of the World. The company publicly committed to paying financial compensation and since then has paid settlements to those with proper claims.

“In some disputed cases, it has made commercial sense to come to a settlement agreement before trial to bring a resolution to the matter. As we reach the tail end of the litigation, NGN is drawing a line under the disputed matters.

“The civil proceedings have been running for more than a decade and deal with events 13-28 years ago. It is common practice, and indeed encouraged in litigation, to seek to settle claims outside court where both parties agree without the cost of a trial.”