I have a whole book of Ladybird Books. For those of you born too late or too focused on stateside books, Ladybird published children's books - usually little hardcover books. The books were designed to introduce children to reading. In the 1970s, when those in my collection were published, it included books like Helping with Mother, Let's Visit the Zoo. They were written on the level of Jack and Jane (or simpler), but the illustrations were far nicer. There was also a series of rhyming stories, of which this volume - The Runaway - is one.
The Runaway was my favorite. The story itself is about a hutch rabbit who, you guessed it, runs away to the forest. Considering the time period, the book is somewhat ahead of its time. The illustration makes it quite clear that the rabbit is the same as a wild rabbit, so while the boy does not mean any harm by keeping a pet rabbit, there is a slight sense of wrongness. But the story ends with both the boy (who has a domestic rabbit) and the rabbit both happy.
Perhaps this story is why I love Watership Down.