I already tried posting this once, but it came out like a fine whine. Let's see if this is better:
The greatest virtue of the movie Goodbye Christopher Robin is that it's rather dull and slow-moving. With luck, it will soon be forgotten and not muddy the already murky waters of confusion any further. It's part meticulous, but mostly Make Stuff Up. Shall we count the ways?
Movie: A.A. Milne witnessed terrible things on the front lines in WW1.
Reality: True. He was on the Somme about three months. He was actually in the same area at the same time as J.R.R. Tolkien, with the same rank doing the same job (signals officer); they were invalided for the same reason (trench fever) and came back to England at the same time, though I couldn't find out if it was on the same ship. The movie doesn't invent them meeting; it missed a bet there.
Movie: After the war, Milne suffered from terrible attacks of PTSD.
Reality: In Movieland, WW1 veteran = PTSD. Not inevitably in reality. What's more, when Milne later wrote about having seen men killed in front of his eyes, he wrote with the same whimsical cheerfulness that he wrote about everything else.
Movie: And writer's block.
Reality: Writer's block? A.A. Milne? Don't put me on.
Movie: So he moves with his family out of the pressure cooker of London to a home in the country.
Reality: They didn't move. They lived in London. The country home was for weekends and holiday getaways, as well-off Londoners have long done.
Movie: His wife, Daphne, is a blunt and outspoken person.
Reality: True, though I know of no source for any of the specific examples in the movie.
Movie: They have a small son whose name is Christopher Robin, but they call him Billy Moon.
Reality: Christopher Milne tells us in his memoir The Enchanted Places that "Billy Moon" was a rare appellation. He was called Billy until about the age of 5. After that his father - and others, but apparently not his mother - called him Moon.
Movie: They hire a nanny named Olive who used to work for the Chilean ambassador.
Reality: True, intriguingly enough.
Movie: A.A. still can't write, so Daphne threatens to leave him.
Movie: So - though he's uncomfortable with small children -
Reality: True, though the depiction of him as unsure what to do with a crying baby is probably invented.
Movie: He makes friends with his son with a deliberate plan to develop material.
Reality: Opposite of the truth. He didn't have the knack with small children, remember? He observed his son carefully, but mostly from a distance. As for why children's books, he later explained there wasn't a plan: he's already a protean writer, why not write whatever comes to hand?
Movie: The name "Winnie," short for Winnipeg, comes from a Canadian bear at the zoo.
Reality: True. "Pooh" and "Moon" came from where the movie says they did too. And they really did play Poohsticks.
Movie: The books are wildly successful.
Reality: True. Milne was rather dismayed at having suddenly turned from a famous adult dramatist into a famous children's writer, which the movie doesn't get into.
Movie: There are incessant interviews and photo ops, which the boy hates.
Reality: He often enjoyed these, and his parents kept them under tight control.
Movie: He's devoted to his nanny Olive, and even asks her to marry him instead of her fiancee.
Movie: She doesn't like being compared to Alice in the books.
Reality: Christopher Milne doesn't say what Olive thought of it, but he's emphatic that she was caring and attentive, not like the distracted Alice.
Movie: Her departure is dramatic and heartbreaking.
Reality: Nonsense. The fiancee was no secret. CRM was nine and went off to boarding school, that's all. He just didn't need a nanny any more. It's a normal part of growing up.
Movie: His boarding school life is literally nothing but merciless, brutal teasing; he calls it "hell."
Reality: He tells us that Christopher Robin's "appearances at school were few. Mostly we were occupied with other things." He did get teased on occasion, and he found this painful, though he says nothing about being thrown downstairs. It didn't bother him to have Christopher Robin mentioned when teasing was not the intent. "But mostly I had other things to think about and didn't bother about being Christopher Robin one way or the other."
Movie: His father ignores him once the books are written.
Reality: Opposite of the truth. As he grew out of nanny-age, son and father became extremely close. The movie's scene of the father teaching his son not to hold his utensils trencherman-style really happened, though in CRM's telling AAM is much wittier than he's shown in the movie.
Movie: CRM joins the army to get away from being Christopher Robin.
Reality: More nonsense. At that stage he had no resentment. He joined, he says, out of a general patriotism that felt Hitler was worth fighting against, a feeling that his father, though he'd previously called himself a pacifist, fully shared.
Movie: A telegram reports him missing presumed dead.
Reality: It said he had been wounded, hit by a shell in the head. It didn't say not seriously. His parents were, naturally, deeply concerned. They were very proud when they heard how calmly he'd taken it.
Movie: After CRM returns from the war, father and son have a reconciliation.
Reality: This is actually when the break occurred between them. CRM had a hard time establishing himself in a career, and became bitter about his father having achieved fame and fortune on his son's back. But the bitterness was never total, and it didn't last. In later life he always disliked being Christopher Robin, but it never dominated his life: he came to terms with it and was willing to discuss it; eventually he even wrote that book explaining the history.
Movie: AAM's biographer Ann Thwaite is listed in the credits as a consultant.
Reality: The posters say "Inspired by a true story." Inspired, but only loosely based on.