A US judge has asked for Prince Andrew’s former assistant, Robert Olney, to give evidence as part of the civil sex assault case brought by the duke’s accuser Virginia Giuffre.

Court documents reveal Judge Lewis A Kaplan has written to both the Senior Master of the Queen’s Bench Division and the Australian attorney general to request their assistance in acquiring evidence for the civil claim filed by Ms Giuffre.

In a separate letter to the High Court, the judge has also requested testimony from a woman who claims to have seen Andrew in Tramp nightclub in London.

The Duke of York has strenuously denied all the allegations.