Paul Dacre, who previously edited the Daily Mail, is set to appear as an early witness when Associated Newspapers Limited faces a High Court trial over allegations of illegal information gathering.
The case has been brought by Prince Harry and six others, including Sir Elton John, David Furnish, Liz Hurley, Sadie Frost, Baroness Doreen Lawrence and Sir Simon Hughes.
It is scheduled to begin on January 19 before Mr Justice Nicklin.
The claimants allege that ANL engaged in or arranged unlawful methods to obtain private information.
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These include claims that private investigators placed listening devices in cars, used deception to obtain confidential documents and accessed telephone communications without authorisation.
The Daily Mail publisher strongly denies the allegations, describing them as preposterous.
The company continues to reject any suggestion of wrongdoing.
Mr Dacre, who now serves as editor-in-chief at DMG Media, is expected to be called first by ANL.
Former Daily Mail editor named as key witness in Prince Harry case
|GETTY
The publisher’s KC, Antony White, said it is incredibly important for various reasons that Mr Dacre and Peter Wright give evidence at the outset so they can address what he described as critically important allegations before other witnesses appear.
Mr Wright previously edited the Mail on Sunday.
David Sherborne, representing the Duke of Sussex and the other claimants, said ANL intends for Mr Dacre to give evidence relating in part to material from his appearances at the Leveson Inquiry in 2011 and 2012.
Mr Justice Nicklin cautioned the claimants’ legal team against allowing the trial to become a wide-ranging public inquiry focused only on selected issues.
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Paul Dacre leaving the High Court after giving evidence to the Leveson inquiry into media standards in 2012
|PA
He also warned that he would not permit attempts to surprise witnesses or catch them unprepared.
The court granted limited access to notebooks belonging to private investigator Stephen Whittamore.
These records set out work carried out for journalists and were retained by ANL after the Leveson Inquiry.
Mr Sherborne argued that the restricted access placed his clients at an unfair disadvantage.
Barrister David Sherborne arrives at the Royal Courts of Justice in October
|PA
Separately, private investigator Gavin Burrows has withdrawn a witness statement, claiming his signature was forged.
Mr Sherborne dismissed this allegation as scurrilous and an attack on the legal team.
The trial is expected to last nine weeks.