Watching the Powell family in the park, there’s nothing unusual about them. Parents Kathryn* and Mark chat, keeping a close eye on Jack, nine, and Ruby, seven. But although Ruby – in a Hello Kitty T-shirt, clutching a doll – looks like any seven-year-old girl, two years ago the same scene would have shown Rudy, a five-year-old boy.

Thanks to the likes of Caitlyn Jenner and Orange is the New Black star Laverne Cox, the term transgender has recently moved into the mainstream. But they are adults. What’s it like for a mother whose child makes it clear they don’t feel they were born with the ‘right’ body?

For Kathryn, it was obvious early on that Rudy was not like his elder brother. ‘Jack was naturally boyish. So when Rudy preferred playing with my jewellery to toy cars as a toddler, I thought, “He’s just a different kind of boy. Maybe he’ll be gay.”’As soon as he was able to decide, Rudy would quietly show a preference for playing with girls, and for girls’ clothes.