The Hundred Acre Wood is set to become just a little bit bigger.

A brand new addition to the world of Winnie-the-Pooh has been unveiled ahead of the 90th anniversary of the publication of AA Milne's original set of stories. Inspired by a photograph of the author and his son Christopher (Robin) Milne with a toy penguin, the character will join young Christopher Robin and his friends Pooh, Piglet, Eeyore, Owl, Rabbit, Kanga, Roo, and Tigger.

Penguin will make a first appearance in short story In Which Penguin Arrives in the Forest, penned by Brian Sibley; one of four seasonal tales included in the authorised sequel The Best Bear in All the World, set to be published this October. Sibley was inspired to create the character after spotting the penguin toy in the photograph of Milne and Christopher playing on the nursery floor with the same teddy bear which inspired Winnie-the-Pooh himself.

"For someone who has loved Winnie-the-Pooh and co from his earliest childhood, the idea of visiting Hundred Acre Wood in search of a new story was wildly exciting," he said. "However, having studied and written about the works of A.A. Milne, it was also daunting. But, for me, the challenge was more than just attempting to play A.A. Milne in his own literary game. I also wanted to find a way of successfully introducing a brand new character into Pooh's world, whilst being sympathetic to the tone and style of the original books."

"The thought of Pooh encountering a penguin seemed no more outlandish than his meeting a kangaroo and a tiger in a Sussex wood, so I started thinking about what might have happened if, on a rather snowy day, Penguin had found his way to Pooh Corner."

Rupert Hill, trustee at Pooh Properties, said: "The character of Penguin, based on a real toy that Christopher Robin played with in the nursery, is a perfect addition, very much in keeping with the classic books and a fitting homage to A.A. Milne's deft characterisation."

Like other characters - Pooh, Eeyore, Kanga, Roo, and Tigger - which inspired Milne's stories, the penguin toy is also thought to have been originally bought from the Harrods department store.

"The toy department where Mrs. Milne bought the iconic bear hosted a huge array of stuffed animals," said Harrods archivist Sebastian Wormell. "In the early years of the 20th century, toy penguins soared in popularity as the exploits of Antarctic explorers such as Shackleton and Scott fascinated the public. We believe that the toy pictured could be Squeak, which originated in our 1922 catalogue and came from Pip, Squeak, and Wilfred, a popular cartoon-strip."