Mr Dalrymple contacted police who had agreed the "ruse"
A trial has heard about a ruse which put undercover police on the trail of a stolen Leonardo da Vinci painting.
An expert on recovering stolen art has been giving evidence in the case of five men accused of holding the masterpiece to ransom for £4.25m.
Loss adjuster Mark Dalrymple told a court how a plan swung into operation after he received a "deceptive" letter.
All five men deny attempting to extort money for the safe return of the Madonna of the Yarnwinder.
The High Court in Edinburgh was told about a note from a law firm in the north of England seeking to negotiate a reward for its clients in helping to "repatriate" the painting.
It was e-mailed to Mr Dalrymple four years after the artwork was stolen from Drumlanrig Castle on the Duke of Buccleuch's Dumfriesshire estate.
His reaction was to telephone Det Insp Gary Coupland, who was then leading the hunt for the robbers.
"I think the police felt it was more likely to enable them to progress their investigation if the insurers and myself were to be neatly taken out of the equation," said Mr Dalrymple.
He said the plan was that an undercover officer, using the pseudonym John Craig, would make contact with solicitor Marshall Ronald, one of the men now on trial.
"We had already agreed if there were any future or further inquiry there would be a ruse," he added.
The story was to be that Mr Dalrymple had fallen out with Mr Craig. Mr Craig had quit his job but might still get involved.
"If he (Ronald) wanted to pursue the matter he should contact Mr Craig directly, who was acting for the Duke of Buccleuch," he said.
Mr Dalrymple admitted he was "perplexed" that solicitors should think there was a legal way to repatriate the painting.
He said the practice was for a reward to be offered for the safe return of such a treasure but only after police had approved the deal to ensure that no money was being paid to criminals.
He said no figure was ever put on how much might be paid for the Madonna of the Yardwinder but revealed in court it would be of the order of £50,000 to £100,000.
Mr Dalrymple said that during his years as a loss adjuster there had been only half a dozen art thefts comparable to the Drumlanrig Castle robbery.
He had been involved in securing the return of Turner works stolen from an art gallery in Frankfurt, Germany and a Titian taken from the Marquis of Bath.
On trial are Marshall Ronald, 53, Robert Graham, 57, and John Doyle, 61, all from Lancashire, Calum Jones, 45, from Renfrewshire, and David Boyce, 63, from Lanarkshire. They are not accused of the robbery.
They have denied conspiring to extort £4.25m and an alternative charge of attempted extortion.
The offence is alleged to have taken place between July and October 2007.
The trial continues.