The original memorial between Prince Charles Edwart Stuart and Lord George Murray, the Jacobite lieutenant general and military strategist during the 1745 Rising, has been found in the collection at Blair Castle, the family seat of the Scottish soldier.
The candid correspondence, which outlines the deteriorating relationship between the two, will go on show at the castle’s new Jacobite exhibition, which will tell the story of a family divided over many decades by the campaign to restore the Stuarts to the British throne.
While a transcript of the correspondence has long been held in castle archives, the original has emerged in a batch of papers recently returned to the collection.
Keren Guthrie, castle archivist, said: “To have the original, it just takes your breath away.
"To have this important memorial from Lord George Murray and then to also have Bonnie Prince Charlie’s reply is just remarkable.
"It completes the story and it also gives us an idea as to how completely at odds the two men had become.”
Written in January 1746, the letter was sent to the Prince in the aftermath of the retreat from Derby – a move vociferously backed by Lord George and members of the Council of War but considered a fatal blow to the success of the campaign by Charles.
On January 6, Lord George wrote to the Prince, proposing he should call a ‘Council of War’ from ‘time to time’ and that all operations should be decided by majority.
The letter came weeks after Lord George resigned his position of command, choosing instead to fight alongside volunteers, in the ultimate statement of his belief in the Prince.
The Prince wrote back the very next day.
He said: “When I came into Scotland, I knew well enough what I was to expect from my Enemies, but I Little foresaw what I meet with from my Friends.
It added: "My Authority may be taken from me by violence, but I shall never resign it Like an Ideot (sic) .”
The Jacobite risings split the Murrays of Atholl over years.
The 1st Duke of Atholl, the father of Lord George Murray, was not a Jacobite but his sons - George, Charles and William – commanded a regiment of Atholl men at Braemar in 1715 in the failed attempt to restore the exiled James VIII to the throne.
The Duke, in order to prove his loyalty to the Crown, disinherited William and appointed his second son, James, as heir.
In August 1745, William and the Prince landed in Scotland to begin the rising.
Lord George besieged Blair Castle with cannon fire in March 1746 after it was occupied by the British Army and wrote to William: “I hope you will excuse our demolishing it”.
His brother replied he had “no concern” given the “public service which requires we should sacrifice everything”.
The siege ended when Lord George was recalled to Culloden.
Ms Guthrie said: “This shows you how much of a soldier Lord George was. Even if he didn’t believe in the Prince’s ability to lead, he did believe in the cause.”
A Family Divided opens at Blair Castle to the public on April 28.