The Butterfly Lion by Michael Morpurgo.
The Butterfly Lion (1996) is a lyrical, moving story of an extraordinary friendship between a boy and a white lion — and how that friendship echoes across generations and continents.
The novel is narrated by an adult remembering a childhood meeting with an elderly woman at a French chateau. She tells him the story of Bertie — a story connected to that very house.
Bertie grows up on a farm in South Africa in the early 20th century. Alone and unhappy, he befriends an orphaned white lion cub he calls Bertie — the lion rescues the boy from loneliness. But when Bertie goes to boarding school in England, the white lion is sold to a travelling circus. Bertie never forgets the lion. When he grows up and fights in the First World War, he is befriended by a French girl, Millie, whose family owns a chateau — the very chateau he had told the lion he would one day visit. After the war, Bertie buys the white lion from the circus and brings him to live at the chateau. The lion dies happy but Bertie and Millie grieve deeply.
After the lion dies, white butterflies settle on the hillside in the shape of a lion — a natural memorial that endures. The chateau's hillside still shows this butterfly lion today.