He’d suggested to Louisa that she write a family book for girls. She hadn’t been very enthusiastic at first, unsure that anyone would be interested, but wrote it nevertheless, basing the girls in her story on herself and her three sisters. It proved an astonishing success.

Like many publishers, Thomas Niles was keen to capitalize on a winning formula. He suggested his new author Susan Coolidge might write a similar domestic story, using herself and her own siblings for inspiration. Presumably she was happy to go along with this proposition.

She was a very tall woman, and had been a lively tomboy as a child, just like Katy. She fictionalized her sisters Jane, as gentle but wily Clover, and Elizabeth, as sad left-out Elsie. Her youngest sister, Theodora, became rosy-cheeked John (Joanna), who memorably dotes on a little yellow chair called Pikery, dosing it liberally with medicine when it feels poorly. Her brother William and cousin Theodorus became little Phil and the delightfully greedy and forgetful Dorry.

What Katy Did became almost as successful as Little Women. Susan Coolidge wrote several sequels about Katy, just as Louisa M. Alcott did with her March sisters. What Katy Did at School is almost as good as the first book, mostly because of a naughty new character called Rose Red, but the other books stop being interesting when Katy is grown up, and has lost most of her childhood liveliness. Susan Coolidge wrote short stories about the Carr children too – Johnnie features in a short story in the collection Nine Little Goslings. I wish she had written more about the most interesting of the Carr children after Katy herself, eight-year-old Elsie.

Poor little Elsie was the “odd one” among the Carrs. She didn’t seem to belong exactly to either the older or the younger children. The great desire and ambition of her heart was to be allowed to go about with Katy and Clover and Cecy Hall, and to know their secrets and be permitted to put notes into the little post-offices they were forever establishing in all sorts of hidden places. But they didn’t want Elsie and used to tell her to “run away and play with the children”, which hurt her feelings very much.

Susan Coolidge goes on to write that in ‘almost every large family, there is one of these unmated, left-out children’. I wonder if she and her sister Jane ever had secrets from their younger sister Elizabeth?

I’ve frequently chosen What Katy Did when asked to write about my favourite childhood book. I’ve also written my own modern version, simply called Katy. I’m usually wary of the current trend of rewriting or embellishing the classics, great or small, but I felt there was some point in attempting this twenty-first-century version. Susan Coolidge deals with illness and disability in a problematic way, though of course authors can only reflect the times they’re living in.

Most nineteenth-century people believed in an all-powerful God with miraculous healing powers. The disabled were encouraged to be as saintly as possible in the hope of being granted some kind of heavenly cure. Katy’s cousin Helen has some unspecified illness that means she’s a permanent invalid, unable to walk. The children are excited when they are told she’s about to visit, but worry she will be very serious and religious. Clover fears she will want them to sing hymns all the time, and Katy thinks she will read the Bible a great deal. In actual fact, Cousin Helen is no saint in a frilled wrapper – she’s jolly and stylish and enormous fun.

When Katy has her accident and becomes an invalid herself, she is understandably wretched and tearful and impatient. Cousin Helen pays her a special visit and is kind and tactful and understanding, but her suggestion that Katy should cope by joining God’s School of Pain makes me squirm. The Victorian idea that invalids should be patient and cheerful and make the best of things would possibly infuriate some wheelchair users nowadays.

Katy tries hard to do as Cousin Helen suggests and her whole character gradually changes. ‘Not that Katy grew perfect all at once. None of us do that, even in books’, Susan Coolidge writes, a nice touch – but Katy eventually grows sweet and saintly, even becoming a little mother to her siblings when poor Aunt Izzie sickens and dies. It isn’t spelt out in so many words, but the implication is obvious: Katy has become so good that she’s rewarded by being able to walk again.

I remember being very happy for Katy when I read the book as a child.