David gave us all a lesson in history and plant biology - he had brought along the original Electrolytic Docking Percolator which he designed in 1959.
Its purpose is to allow the study of the way in which soil bacteria break down the nitrogen in fertiliser applied to the soil.
David told us that, shortly after designing the apparatus, he had the opportunity to show it to H.R.H. the Duke of Edinburgh, and later it was featured in Bert Love’s book on Meccano.
Fame indeed! Twice?