She has a strict bedtime of ten p.m. At least, that’s when her parents expect her to be in bed, with no light visible from the crack under her bedroom door. Budding doctors need their sleep. So she gets ready as usual, brushing her teeth and changing into her serviceable cotton pyjamas, but instead of letting herself drift off into a UCAS-inspired stress dream, she recites the periodic table in her head until she’s utterly sure her parents are asleep.