At a secret location on the Somerset Levels, I peer into a deep tank. The air is cool and smells fishy, filters hum. Elvers – each as long as my little finger – squirling through the water in precise calligraphic strokes, like a single letter endlessly repeated. My friend Hannah fishes some out and decants them carefully into a plastic bag like fairground goldfish. These fish are far more precious. Once abundant here on the Levels, they are now critically endangered, and one of the most trafficked animals in the world. We load our precious cargo into the Eelmobile, a van full of tanks, filters and assorted kit, and driven by Hannah Strode, who heads a marvellous initiative called, simply, Eels in the Classroom. She has spent the past few months cold-calling schools, asking if their children would look after baby eels until they are ready to be released. Every single school – 59 of them – came back with a resounding yes. I mean, eels in the classroom? Come on! The life cycle of the European eel is best described as insanely unlikely meets totally random. They hatch in the Sargasso Sea in the North Atlantic – nowhere else on the planet. For their first few years, they look like tiny willow leaves, and were once thought to be a totally different species. These drift wherever the ocean’s currents take them until, at some point, they morph into freshwater-dwelling glass eels – and start to swim upriver, ending up in places like the Somerset Levels. At some point (no one knows what triggers this), they mature into adults, and at some point (no one knows what triggers this either), they swim back to the Sargasso to mate and die. The year 4 children are fizzing with their own questions for the Eel Lady (which sounds like the name of a superhero and, by the looks on their faces, she is one). How many are there? Are they boys or girls? How old are they? Do they sting? Hannah will be back in a few weeks to help with the releases: restocking the rivers above the weirs and sluices that stand in their way. Until then, “the elvers will learn from the children, and the children from the eels. The young teaching the young: what could be better than that?”