During research for the Tattershall Castle Conservation Plan for the National Trust, a set of framed drawings of the castle was found in the storeroom of the great tower. Examination of the Curzon correspondence deposited by the National Trust in the Lincolnshire Record Office revealed that these had been commissioned in 1783 by no less a person than Sir Joseph Banks (of nearby Revesby Abbey), President of the Royal Society and Council member of the Society of Antiquaries. With the help of the Sir Joseph Banks Archive Project, and piecing together materials in Aberystwyth, Cambridge, Lincoln, London and New Haven, Connecticut, a story has emerged of antiquarian endeavour in the 1780s when, amidst a frenzy of scientific activity, rampant balloon mania and the care of an ailing turtle, Sir Joseph commissioned the most detailed survey yet undertaken of a medieval monument in the British Isles, entrusting the task to the hitherto unremarked J L Johnson, surveyor and draughtsman, a figure who deserves belated recognition and a place in the history of medieval archaeology for his pioneering efforts.