The Duke of York and his ex-wife Sarah, Duchess of York, have reached a “settlement” after becoming embroiled in a High Court dispute between a wealthy Turkish woman and a Turkish businessman, a judge has been told.

Andrew’s link to the fight over money between 78-year-old Nebahat Isbilen and businessman Selman Turk emerged last year after written claims were filed.

A judge – Deputy High Court judge David Halpern – who was overseeing the litigation at that stage had been told, in a document written by a lawyer representing Mrs Isbilen, how evidence showed “money was used for purposes unconnected with Mrs Isbilen, eg, substantial sums were paid to Prince Andrew, Duke of York, and to Sarah, Duchess of York”.

An affidavit filed by the lawyer had said Mrs Isbilen “relied on a payment of £750,000 to the personal account of Prince Andrew, which Mr Turk instructed to be made from Mrs Isbilen’s account with Hampden Bank, as a specific instance of dishonest behaviour by Mr Turk”.

Sir Anthony Mann has been told, in written arguments prepared by lawyers representing Mr Turk, that there has been a “settlement” between Mrs Isbilen and the Duke of York, and Sarah, Duchess of York.

James Counsell KC, who is Mr Turk’s legal team, told Sir Anthony in a written case summary that Mrs Isbilen “relies on a so-called ‘agreed statement’, prepared, it is claimed, as part of a settlement between herself” and the Duke of York and Sarah, Duchess of York.

Judges have heard that Mrs Isbilen had needed help moving assets out of Turkey after her husband became a political prisoner, and that Mr Turk had agreed to help.

She alleges that he “breached fiduciary obligations he owed to her” and has advanced “claims in deceit”.

Mr Turk is fighting the case.

The hearing being overseen by Sir Anthony relates to contempt allegations made by Mrs Isbilen.

She alleges that Mr Turk has breached a judge’s order by “failing to disclose a considerable amount of information relating to the whereabouts of certain defined assets”.

Mr Turk disputes claims made against him and says he has “done his best” to co-operate and “attempted to comply with the order”.

The duke’s name appears more than a dozen times in written case summaries, prepared by lawyers on both sides, for the hearing being overseen by Sir Anthony.