Andrew Mountbatten-Windsor can be called to give evidence in a High Court trial involving allegations of fraud against a Turkish businessman, a judge has ruled.
Nebahat Isbilen, a Turkish national, alleges that Selman Turk, her former adviser, misled her over a £750,000 payment made to Mountbatten-Windsor in 2019.
The judge agreed to allow Turk, who denies dishonesty, to seek to call evidence from Mountbatten-Windsor in a trial in London expected to begin in November.
Mountbatten-Windsor repaid the money, and there was no suggestion of wrongdoing by the former Duke of York.
Ahead of the trial, Turk made a bid to be allowed to call Mountbatten-Windsor to give evidence.
In a judgment on Friday, Justice Adam Johnson agreed, allowing Turk to rely on a witness summary and seek to call evidence from the former duke.
Johnson said: "Given the seriousness of the allegations, both on their own terms and in light of their wider impact, fairness requires that Mr Turk should be afforded an opportunity of putting forward his own case, using the evidence he considers relevant and material."
The judge later said that his decision meant Turk could call evidence from the former duke, but that a witness summons "will likely" be needed to compel Mountbatten-Windsor to give evidence.
Johnson added: "It is highly unlikely that a person in the position of Mr Mountbatten-Windsor would wish voluntarily to provide a witness statement and give evidence at a trial in public proceedings involving payments made by the wife of a person said to be a political prisoner in Turkey, in connection with a dispute about the reason the payments were made."
Isbilen, who in 2022 was 77 years old, is from a wealthy family, but when her politician husband was jailed she wanted help moving her assets out of Turkey.
Lawyers for Isbilen previously told the court that tens of millions of her funds had been misappropriated, with Turk failing to explain where the money had gone.
In Friday's ruling, Johnson said it "has long been Mr Turk's case" that the £750,000 payment was made on Isbilen's own accord as she believed Mountbatten-Windsor could help with her husband.