After he graduated from Cambridge in 1903, Milne pursued a writing career, submitting poems and essays to Punch magazine, and eventually becoming an assistant editor there. Meanwhile, he was writing. He produced three novels and 18 plays. His murder mystery The Red House Mystery (1922) was popular, and critic Alexander Woollcott said it was one of the three best mysteries of all time. Mystery writer Raymond Chandler didn't agree. He said it was agreeable and amusing but had an illogical plot. In any case, it was the only mystery Milne ever wrote.
After his son, Christopher Robin Milne, was born in 1920, Milne began the Pooh books and the poetry. All the famous characters in the Pooh book — Piglet, Eeyore, Tigger, Kanga, Roo, Owl and Rabbit — were inspired by Christopher Robin's stuffed animals. The Hundred Acre Wood, where Pooh and his friends lived — came from Five Hundred Acre Wood in Ashdown Forest near the Milne home in East Sussex southeast of London. Tigger was introduced in the The House at Pooh Corner. He is known for his pronouncement that "bouncing is what Tiggers do best."
Winnie-the-Pooh is named after a Canadian black bear that served as a military mascot during World War I. The bear, who was called Winnie for the Canadian city of Winnipeg, stayed at the London Zoo during the war. The Pooh part came from a swan with that name.
Milne also wrote films for British actor Leslie Howard's company, Minerva Fiims. Milne met Howard when the actor was starring in a London production of his play Mr Pim Passes By. Milne was determined to write whatever he wanted to despite the popularity of his children's stories and verse. His agent told him he ought not to write detective fiction and other genres. "I should be as proud to be delivered of a Telephone Directory con amore as I should be ashamed to create a Blank Verse Tragedy at the bidding of others," Milne wrote.