A Turkish businessman accused of “deceit” during a High Court dispute in London with an elderly Turkish woman appeared at a charity event hosted by the Duke of York at St James’s Palace, a judge has been told.

Selman Turk had “sought to promote his UK banking business” at the event in November 2019, a solicitor representing Nebahat Isbilen, who is in her 70s, said in a written affidavit filed during the litigation.

Andrew, his ex-wife Sarah and both their daughters have all been named in the affidavit filed recently by Jonathan Tickner, head of fraud and commercial disputes at law firm Peters & Peters.

The judge overseeing the dispute was earlier told that Andrew was allegedly paid £750,000 for “assistance” provided “in relation” to Mrs Isbilen’s passport.

Deputy High Court judge David Halpern mentioned the duke and Sarah in a recent preliminary ruling on the dispute.

He heard that Andrew had returned the money.

The judge said in the preliminary ruling that he had been told “substantial sums” were paid to Andrew and Sarah.

More detail has emerged in an affidavit filed by Mr Tickner on behalf of Mrs Isbilen with the High Court on March 4.

The duke’s name appears more than a dozen times in the 58-page affidavit.

Mr Tickner also mentions Sarah and Princess Beatrice and Princess Eugenie.

Mrs Isbilen had needed help moving assets out of Turkey after her husband became a political prisoner, Judge Halpern has been told, and 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.

Lawyers representing Mrs Isbilen told Judge Halpern that “total sums” that were “misappropriated” amounted to 50 million US dollars (£38 million).

Judge Halpern said in the preliminary ruling that Mr Turk had provided explanations for approximately two-thirds of “these sums”, but “no explanation at all” had been given for the remaining third.

Mr Tickner told the judge in an earlier document that 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”.

The affidavit filed on March 4 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”.

“Mrs Isbilen’s evidence is that she was told the payment was to be made in connection with obtaining immigration documents,” Mr Tickner added.

“Mr Turk sent emails to an employee of Hampden Bank representing (it is alleged falsely) that the payment was by way of a wedding present for HRH Princess Beatrice of York.

“Mrs Isilen has since obtained transcripts prepared by Hampden Bank of telephone conversations between Mr Turk, Hampden Bank and Prince Andrew’s private office, in which this representation was repeated.

“In fact, Mr Turk appeared at a charity event hosted by Prince Andrew at St James’s Palace on 5 November 2019, at which he sought to promote his UK banking business.

“Mrs Isbilen suspects that the payment was made for some purpose connected with the banking business.”

Mr Tickner went on: “Peters & Peters wrote to Prince Andrew in March 2021, requesting an account of his dealings with Mr Turk.

“Prince Andrew declined to provide any such account but … repaid Mrs Isbilen the sum of £750,000.”

Mr Tickner said in the affidavit Mrs İşbilen had asked for bank records relating to an account in the name of a company called Alphabet Capital Limited to be disclosed.

He said a “pattern of payments” was “consistent with a calculated attempt to facilitate transfers to Prince Andrew and to mask the source of funds”.

Mr Tickner said there were “strong grounds for inferring that the payments from the Alphabet account to Prince Andrew were made at Mr Turk’s direction”.

He added: “Prior to the Alphabet application, Peters & Peters were not aware of any connection between Mr Turk and Sarah, Duchess of York.”

Mr Tickner said bank records for Mr Turk’s accounts showed that, on November 28 2019, $25,000 (about £19,200) was transferred to Mr Turk from a Las Vegas company called Pegasus Group Holdings LLC.

He added: “Online media reports suggest that Sarah, Duchess of York has acted as a brand ambassador for Pegasus Group Holdings.

“It appears, therefore, that there is a connection between Sarah, Duchess of York and Mr Turk (although the reason for his receiving an apparent payment on account of her fees is difficult to explain).

“At least £225,000 was transferred to an account in the name of ‘DUCHESS OF YORK’ out of the Alphabet account … in regular instalments and in most cases under the reference ‘PEG001’. This reference may be related to Pegasus Group Holdings.

He went on: “As with the payments to Prince Andrew, there are accordingly strong grounds for inferring that these payments were made at Mr Turk’s direction.”

Mr Tickner also referred to a £15,000 “birthday gift” payment to “Eugenie York”.

“Prior to the Alphabet application, Peters & Peters were not aware of any connection between Mr Turk and HRH Princess Eugenie,” he said.

“The bank records … for Mr Turk’s account show that, on October 10 2019, Mr Turk made a payment of £15,066.05 to ‘Eugenie York’ under the payment reference ‘Birthday gift.’”

He said there was a “basis” for inferring that “this payment was made to HRH Princess Eugenie”.

Mr Tickner added: “For similar reasons to Prince Andrew and Sarah, Duchess of York, there are strong grounds for inferring that this further payment was made at Mr Turk’s direction.”

He indicated that Mr Turk was arguing that the “transfers to the Duke of York were not made on a fraudulent basis”.