After the cost of building the Auld Hoose, the Governors had to wait for a return on their investments before they could afford to admit pupils. As a result, the building lay empty when the Duke of Cumberland passed through Aberdeen in 1746 in pursuit of the Jacobites. He decided to use it to garrison some 200 of his troops and the Hospital was converted into a temporary fort, surrounded by a ditch and protected with a palisade. The garden walls were taken down and a well was dug in the grounds. A considerable amount of damage was also done to the interior and the Governors had to put in a claim for the cost of repairs to the King, which was paid in October 1747.