Sarah Knight was stressed. She was home with a six-month-old baby, breastfeeding, adjusting to her new responsibilities as a mother. She was doing her best, but something seemed off. Her son Will was suffering from eczema, acid reflux and, more alarmingly, didn’t seem to be putting on weight. She and her husband Ian had been taking him back and forth to the local surgery pretty regularly, for one reason or another. They’d been referred to a paediatrician, and started topping-up his feeds with a bottle. But Will refused, spitting the milk back out. It was driving Sarah crazy.