The Prince of Wales praised Muammar Gaddafi and told him he was "heartened" by the way relations between Libya and the United Kingdom were developing in a letter to the former dictator, it has been reported.
Heir to the throne Charles wrote to the deposed leader on June 7 2007, calling him "Your Excellency" and commending his work with Christians and the British Council, according to The Times.
Royal sources said the letter, sent on the advice of the Government, was aimed at helping secure the release of six Bulgarian medical workers who were falsely imprisoned in Libya for infecting children with HIV.
Referring to finding a "satisfactory" solution for the families of the affected children, the Prince wrote: "I have no doubt that this will have a further positive impact on the friendship between our peoples."
The five nurses and one doctor, who served eight years of their life sentences and always maintained their innocence, were released in late July 2007 following years of international negotiations.
The letter, typed on Clarence House note paper, was written the week after a visit by the then prime minister Tony Blair and was found in a palace belonging to Gaddafi's son Saif al-Islam, The Times said.
Charles wrote in the correspondence that he had been briefed on Mr Blair's visit and on "the positive way" in which relations between Libya and the United Kingdom were heading.
He added: "I just wanted to write to Your Excellency to say how heartened I am by the breadth of these developments."