Some people would say that my second son is stupid. I understand what they mean. But it’s a word that I’ve come to use less casually than most. Just a few days before the opening ceremony for the Paralympic Games, he had a pretty significant birthday. But while most boys would have celebrated turning 16 by tasting the forbidden fruits of adult life and drinking too much cheap cider, Joey blew out the candles on his birthday cake with a giggle of excitement, jumped up and down with pleasure unwrapping the presents he’d been given and went to bed – entirely sober – at 7pm.

Because, you see, Joey is very different from most 16-year-olds. He has profound and multiple learning difficulties. His condition is still undiagnosed, although it’s almost certainly the result of a genetic glitch. He’s an attractive boy, with a shock of brilliant blond hair and a dazzling smile. But he’s very small, sometimes painfully thin and suffers from severe epilepsy. His coordination is poor and he’s extremely timid. He’s terribly vulnerable and when the epilepsy is bad, he’s pitiful. Most significantly, he has very restricted cognitive abilities and only a limited understanding of what is going on around him. He communicates in rudimentary Makaton sign language (and makes noises with a clear commitment to what he wants) but has never uttered a single word: not “mum”, not “dad”, nothing. What at first was termed “developmental delay” is now quite clearly a profound and serious learning disability.