Sandby visited Tantallon Castle as part of his work for Roy’s Military Survey of Scotland. The study was the first ever systematic survey of mainland Scotland to be carried out and Sandby, through his position with the Board of Ordnance, was chief draughtsman on the project. Tantallon Castle, located close to North Berwick, is a fortress dating from around 1374. It is spectacularly positioned on a cliff opposite the Bass Rock, with impenetrable sea cliffs on three sides and a massive curtain wall and towers on the landward side.