Having been educated in Jacobite and Episcopalian principles, young Johnstone hailed with delight the arrival of Prince Charles: he resolved instantly to join his standard. Escaping from Edinburgh, he hastened to Duncrub, the seat of Lord Rollo, near Perth. Here he awaited the arrival of the young Chevalier; and here he was introduced by his cousins, the daughters of Lord Rollo, to the Duke of Perth and to Lord George Murray. The Chevalier Johnstone was one of the first Low-countrymen that joined the standard of Charles Edward. Lord George Murray very soon discovered that the requisites for forming a good soldier and an active partizan were centred in young Johnstone. For the former he was qualified by an open and impetuous character, generally combined with a desperate courage. The jollity and licence of the Cavalier school, which characterized Johnstone, did not materially detract from, but added rather to the popularity of his character. As a partizan, he has proved his zeal by his Memoirs, which afford a sample of much heat and prejudice, and which have, in upholding Lord George Murray, done an injury to the memory of Charles Edward, of which the adversaries of his cause have not failed to take advantage. To many errors of character, and to some egotism, the Chevalier Johnstone, as he came to be called in after-life, united a kind heart and an enthusiastic disposition. He acted for a considerable time as aide-de-camp to Lord George Murray, and afterwards in the same capacity with the Prince. But his liveliest admiration appears to have been directed towards the general who has been classed with Montrose and Dundee,[28] and no subsequent service under other masters ever effaced his impression of respect and confidence to Lord George Murray. After the battle of Preston-Pans Johnstone received a captain's commission from the Prince: and, exhausted with his duties as aide-de-camp, he formed a company, with which he joined the Duke of Perth's regiment. His history, mingled up as it is with that of the General under whom he first served, must necessarily be incorporated with the following narrative. Lord George Murray continued, for some time, busily engaged in rallying around him his brother's vassals. The Duke of Atholl is partly proprietor, partly superior, of the country which bears his name. That region is inhabited by Stuarts and Robinsons, none of the Duke's name living upon his estates. Of these, several have fiefs or mortgages of the Atholl family, and command the common people of their respective Clans; but, like other Highlanders, they believe that they are bound to rise in arms when the chief of their whole Clan requires it. The vassals on the Atholl territory were well-affected to the Stuarts, great pains having been taken by the father of Lord George Murray, notwithstanding his efforts to appear loyal to the Government, to infuse the spirit of Jacobitism among them.[29]