A struck-off lawyer is suing a Scottish aristocrat for £4.25 million following the theft and recovery of a Leonardo da Vinci painting stolen from a castle.
Marshall Ronald is pursuing a similar claim against the chief constable of a Scots police force that led the hunt for the missing masterpiece.
Mr Ronald was acquitted with others of a conspiracy to extort £4.25m for the safe return of the masterpiece at a trial at the High Court in Edinburgh in 2010.
The Madonna of the Yarnwinder was stolen from the Duke of Buccleuch's Drumlanrig Castle, Dumfriesshire, in 2003.
A covert operation eventually led to its recovery following a meeting at the offices of a law firm in Glasgow on October 4, 2007. Mr Ronald and others who had attended were detained.
He is now pursuing a compensation claim in the civil courts against the Duke of Buccleuch and Chief Constable Patrick Shearer of Dumfries and Galloway.
He claims that under the terms of an alleged contract between him and an undercover officer, known as John Craig, it was agreed he would arrange for the return of the painting in return for sums totalling £4.25m.
He maintains some of the money was being paid to people who could assist in the painting's recovery and £2m being transferred to a Swiss account in the name of Mr Ronald.
The duke and Mr Shearer are both defending the action at the Court of Session in Edinburgh. The duke denies entering such a contract and maintains any alleged contract would be unenforceable as being illegal and contrary to public policy.
During a hearing senior counsel for the duke described it as "a hopelessly irrelevant case" and the QC acting for the senior police officer said the summons was "plainly irrelevant and quite frankly nonsense".
Alan Cowan, for Mr Ronald, told the court a legal aid application had been made but a decision was not expected until March and sought to have a stay put on proceedings until then.
Maria Maguire, QC, for the chief constable, told the court: "It is patently obvious that John Craig was an undercover officer who was acting at all times within that role.
"It cannot be possibly held with any degree of credibility he was at any time acting as an agent of the Duke of Buccleuch or that he was entering an agreement on behalf of the chief constable of Dumfries and Galloway with this individual."
She said there was a provision in legislation for police acting under authorisation in such roles being excluded from civil liability. She said there was no suggestion the conduct was unauthorised or unlawful.
The court heard Mr Ronald,56, of Lancashire, was struck off as a solicitor. A disciplinary tribunal said he allowed himself to become involved in "a dubious transaction".
During his trial two co-accused, Robert Graham and John Doyle, were also acquitted. They ran an online business, Stolen Stuff Reunited, and had been contacted by an intermediaries of those holding the painting. They consulted Mr Ronald.
Lord Doherty said he was not prepared to exercise his discretion to put a stay on the action and awarded expenses against Mr Ronald.