A spotter's guide to Caucasian wingnuts

"From pollination to the Caucasian wingnut's first released seed you could have taken 28,478,544 steps." Message set into a paving stone outside the Network Rail building, Milton Keynes.

The Caucasian wingnut (AKA the Caucasian walnut), Pterocarya fraxinifolia, is a deciduous tree, native to the Caucasus/Iran region. Apparently, it can grow up to 20m high, bears small green winged nutlets and its dark wood is often used in veneers, so it can't, unlike certain other Caucasian wingnuts I could mention, be accused of being neither use nor ornament.