On a small island in the Thames, five silver-grey pyramids emerge from the surrounding trees and undergrowth, forming a linear structural rhythm that resonates with the Gothic silhouette of Eton College Chapel in the distance. At close quarters, standing in the outdoor anteroom underneath the first pyramid, the building starts to be understood as a unique construction – the walls are simply large interlocking blocks of solid cork, in which structure, insulation, external surface and internal finish are all one and the same thing.