George Hay was born in Edinburgh on 24 August 1729 into a family of the Scottish Episcopal Church. He began medical studies at the University of Edinburgh. During the Jacobite rising of 1745, when he was only sixteen, he attended to wounded soldiers after the battle of Prestonpans, and afterwards followed the Jacobite army of Bonnie Prince Charlie down into England. As the Jacobites returned north, he took ill and returned to his family in Edinburgh. After the defeat of the Jacobite Army at Culloden, he was advised to hand himself into the authorities and confess to his part as a medical orderly. This did not save him from being sent to London to spend a year in a prison ship on the Thames. It was here that a Catholic bookseller named Neighan gave him his first insight into Catholic teaching.