Prince Harry and News Group Newspapers have launched a joint bid to appeal against Mr Justice Fancourt's decision denying a third trial adjournment.
The unusual alliance comes as both parties claim they are close to reaching an agreement through recent negotiations.
The move follows Justice Fancourt's refusal to delay the trial further on Tuesday afternoon.
Anthony Hudson KC, representing NGN, highlighted the rare unity between the parties, stating: "Both parties are in complete agreement. The number of times the parties have been in agreement in this litigation are very few and far between."
Prince Harry and News Group Newspapers have launched a joint bid to appeal against Mr Justice Fancourt's decision denying a third trial adjournment.
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The NGN lawyer also revealed that legal teams had been engaged in "very intense negotiations over the last few days" and were "very close" to reaching a resolution.
While Mr Justice Fancourt denied the parties permission to challenge his decision, he left the door open for them to take the decision to the Court of Appeal.
"I'm not going to stand in the way of access to justice if the parties wish to go to the Court of Appeal," Justice Fancourt said.
Both Prince Harry and NGN retain the option to make their appeal directly to the Court of Appeal.
Prince Harry and NGN retain the option to make their appeal directly to the Court of Appeal.
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In explaining his refusal for a third adjournment, Justice Fancourt stated: "There comes a point where the parties have had ample time to seek to resolve their differences and have not done so."
He added: "I made it clear this morning when granting the second adjournment that it would be the final adjournment. I see no reason to change my mind."
The judge maintained he was "not satisfied" the trial should not proceed at this time.
The trial faced multiple delays on Tuesday, initially scheduled for 10:30am before being pushed back to 11:30am following a request from both sides.
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A second request led to a further postponement, with the trial start time moved to 2pm.
The judge stated that he would not allow any further pushbacks to the start of the trial from 2pm onwards.
Mr Justice Fancourt said: "I am a little concerned about the timetable overall."
He added: "On the other hand an hour or two in the context of eight weeks is not significant.
"If the parties can assure me that time will be beneficial and will produce some outcome, then I am willing to provide some further time - but it has to be the last adjournment."
