I remember on the way home from nursery one December day, my son pointed at a small plastic fish in a charity-shop window. In the next window, I showed him a Christmas tree, and, in a phase when he was obsessed with defining things negatively, according to his own idiosyncratic system of what they were not, he replied: “It’s not a fish!” For at least two more years, every time we saw a Christmas tree one of us would say: “It’s not a fish!” and fall about laughing. I know, the levels of you-had-to-be-there are off the scale, but this is the way with autism. It’s hard to explain, and highly specific. The point is, even with all the challenges – and there are many – if you just open the door of your mind to autism, the world is reborn. And it’s incredible.