‘Excellent answer. Money can’t buy happiness. And what else is it about?’

‘We shouldn’t judge people just because they have something wrong with them, like his fits?’

‘Good answer again. George Eliot was herself a bit of an outsider, because . . .’

Kath didn’t hear the rest of the explanation because she was so startled by the revelation: the author of this book was a woman. Why had she changed her name to a man’s?

Rather than display her ignorance in class, Kath went to the library after school and, perhaps for the first time in her life, headed to the section signed Reference Books. There, she found a long shelf of heavy tomes called the Encyclopaedia Britannica. Taking out a volume bearing the letters E–H, she read the story of a feisty woman called Mary Ann Evans who rebelled against her family, went to London to become a journalist, lived ‘in sin’ with a married man, flouting the disapproval of Victorian society, and finally achieved success and happiness. But she always wrote under a man’s name so that her work would be taken seriously. What a woman, Kath thought.

It wasn’t only English that began to fire her imagination. In the past, any mention of numbers, of multiplication and division or, worse, algebra and geometry, had seemed to freeze her brain. But their new teacher explained everything very simply, with drawings that helped her to visualise what the numbers really meant. After that, if she ever got stuck on a calculation, she could imagine a tree full of apples, and a great wind that blew some of them onto the ground. Or an orchard full of trees and all the boxes of apples at the side after harvest, and how some boxes went to market or were added to the boxes from another farmer, and some rotted, and so on. Somehow she discovered that numbers weren’t so terrifying after all.

Because they were seated in alphabetical order, she found herself sharing a desk with Adam Merriweather, a geeky lad with terrible acne and heavy black-rimmed glasses. What is a clever boy like him doing in revision classes? she wondered. She ignored him at first, before learning from another student that his mother had died just before the summer exams, and he’d failed to turn up for them.

After that she made a special effort to be nice to him, and her friendship was well rewarded: whenever she got stuck with a difficult equation, she would turn to him for help. In class, he would whisper in her ear or write in pencil on the side of her workbook. On a few occasions, she invited him home for tea after school, when Maggie would ply him with tea and cake before they sat down to their homework.

Curiously, the subject she came to enjoy most was the one she’d disliked most before: geometry. Mark, who was obsessed with flying, often talked with Pa about aeroplane design, bandying about terms like ‘vector’ and ‘wind speed’. He would make illustrations with lines and arrows that looked like meaningless doodles, until one day the teacher drew a circle and wrote beside it ‘360 degrees’. She shaded in half of the circle and wrote ‘180 degrees’, halved that once more and wrote ‘90’, then halved again and wrote ‘45’. At last Kath understood what an angle was.