After seeing herself in a friend’s post, Sarah has realised that her teeth are impossibly ugly – huge and gummy.

She practices in front of the mirror, teaching herself to smile without opening her mouth, lips firmly pressed together. It’s not easy. She aims also to keep her lips over her teeth when she speaks.

After a few days Gemma notices that something is amiss. Her daughter seems to be clenching her jaw.

‘Have you got toothache?’ Gemma asks at dinner. ‘It’s a while since you saw the dentist. Let’s see your gums.’

‘Mum! I’m not a baby.’

‘Well would you tell me? If you had a gumboil?’

‘Yes,’ says Sarah, exasperated. Gumboil. Whoever has a gumboil? How ancient is her mother anyway?

At the end of the week it doesn’t look to Gemma as though Sarah is any more relaxed. She refers the matter up the line. Time for Supergranny. Anne invites her granddaughter out for coffee.

At least it doesn’t seem to be about food, Anne thinks, when Sarah asks for sticky date pudding. But she seems to be eating very slowly. Anne watches the cake disappear crumb by crumb and wonders if it’s one of those diets where you make one piece of food last for an hour. She is not privy to Sarah’s latest discovery, that if you eat only tiny amounts at a time then you can slip them past your teeth without your gums showing, using a teaspoon for preference, though that’s hard if it’s roast chicken or something like that.

‘Is everything okay?’ Anne asks. ‘You don’t seem happy.’

Sarah puts down her spoon. ‘I’m fine,’ she says, without moving her mouth.

‘Would you like something else?’

‘Hot chocolate,’ Sarah says. It’s easiest if you don’t use too many words.

Certainly not a diet thing then. That’s a relief, Anne thinks, overlooking the lack of a ‘please’.

She risks a shot in the dark. ‘I’m missing your gorgeous smile,’ she says.

Sarah looks at her grandmother and sees the love, but it’s no help. Because she can also see that her grandmother’s hair is shapeless with dry grey bits sticking out. And her skin is all wrinkly and flaking with brown splotches and red spots. There’s a blackhead on her forehead that Sarah has been wanting to squeeze for months. She can’t believe Gran hasn’t done it herself. Or plucked the white hairs on her chin. And as for clothes … Gran is wearing a polar fleece she’s had forever and baggy jeans that might be fashionable on some other planet, though Sarah doubts it.

Her grandmother means well, but she has no idea. No. Idea.

Later in the day Sarah catches sight of her face in a shop window and sees that her nose, which up until now has not bothered her, is enormous and makes her look like something out of Shrek. She will have to grow her fringe really long.