BELLA came out of her pre-school nursery excited and holding a plastic cup. In the cup was a snail.

That surprised her mum, who had come as usual to take the four-year-old home. Staff at the pre-school door explained that the little girl had found the slimy creature in the playground.

They said that for the rest of the day Bella had observed the shell-lugging gastropod slithering around on leaves in the cup. Staff had warned Bella that prodding the animal would be cruel but, when the slithering slowed, she still found it hard to resist an occasional tap with a leaf stem.

Having decided the snail was a she, Bella had named her Fluffy Florence.

Bella was allowed to get in the car with Florence and, when they got there, Bella proudly carried her new friend into the family home.

She spent the rest of the day scrutinising Florence as the animal wandered around leaves in a Tupperware box. Bella’s little brother, Kasper, joined her in lying on her bedroom floor and feeding cucumber and lettuce to their slow-motion Tupperware captive.

Self-assured Bella delighted in providing commentary for Kasper, aged two. She kept him informed as Florence ate, blinked, and waved impressive tentacles.

Bella may have been entranced by the exotic newcomer but, when it was time for bed, she knew enough about decorum to make a distinction between herself and a snail. The slobbery one would not be sleeping in her bedroom, she decided.

Next morning down on the ground floor poor Florence was still in her Tupperware “house”. I’m not sure how many days Florence remained an involuntary guest, but it was a lot less than a week.

When the time came for her departure, Bella was by then in a close relationship with the snail. She and her passive little bro must have absorbed every intimacy of Florence’s humdrum lifestyle.

Their parents decided that the evening was the best time to set Florence free and so, just before bedtime, their dad took Bella and Kasper to a flower bed in the back garden. He lay the plastic box on its side and, sure enough, Florence set off for the rim at the snail equivalent of a gallop. She was hammering along at an estimated 1fph (one foot per hour) and the children seemed melancholy at her straight-line dash for freedom.

Dad tried to lighten the mood: “It’s quite exciting that we’re letting her go now, isn’t it?”

Bella disagreed. “No, not exciting,” she said. “It’s sad.”

I know the conversation verbatim because their mother videoed Florence’s farewell on her phone and sent it to me on WhatsApp. Bella said she looked forward to seeing Florence again one day in someone else’s garden, and she wondered if Florence would still remember her name. Then Florence was out of the box, and Bella looked disappointed.

“Shall we say bye then, now we’re going to bed?” said Dad. “Do you want to give her one more stroke?” Bella stroked the snail’s shell with one finger.

“Bye bye, Fluffy Florence,” Dad continued. “We love you very much. Thank-you for coming to stay with us.”

Tears began to well up in Bella’s eyes. Then Dad said: “We’ll miss you” and with that the little girl burst into tears.

Perhaps Bella’s wrench from her first pet was part of learning for life, with its painful comings and goings, and even part of preparing for the ups and downs of romantic love.

Bella and Kasper are my grandchildren. A week later my daughter and I took them to look around Guildford Cathedral. In the grass outside they found a snail, and they lay down and watched it waving its tentacles and chewing. Then they found there were lots of snails in that grass. This time Bella said nothing about wanting to take a snail home. She was a little more grown-up.