About 15 years ago I visited a friend living in a rented farmhouse in southern England. It had a huge fireplace (large enough to stand in) that had been retrofitted for a small log-burning stove. Looking up, I noticed the chimney had been blanked off by what appeared to be aluminum sheeting bearing Concorde diagrams: white anodized aluminium with deep blue ink. I wonder if they are still there, and how they got there.