Thursday marked the 75th birthday of Pippi Longstocking, the character created by Swedish author Astrid Lindgren for her daughter's 10th birthday who went on to become one of the most popular characters in modern children's literature.

Lindgren died in 2002 aged 94, and her 34 story books and 41 picture books have sold 165 million copies in more than 100 languages. The adventures of Pippi, the super-strong red-haired 9-year-old with a trunk full of gold, who lives on an island with Mr Nelson the monkey and Old Man the horse, have delighted readers for decades, particularly in China.

As rights manager of the Astrid Lindgren Company, Lindgren's great-grandson, Johan Palmberg, has responsibility for her work and her legacy. He said she could never have anticipated what she was creating when she published her first book.

"There was no overarching story－she just wrote it for her daughter on her birthday, and then wrote more later because they'd gone so well," he explained.

That birthday gift launched Lindgren on a career that saw her win awards worldwide, honored at home on bank notes, and having a children's hospital and even an asteroid named after her.

Pippi's striking untidy appearance, bright red hair and free spirit attitude have made her a timeless pop culture icon.

"People send me images of her from all over the world," said Palmberg. "The other day, I saw her on a T-shirt in a market in Bangladesh, and also a soldier in Croatia with a picture of her."

Pippi's message of honesty and self-belief has also seen her adopted by the charity Save the Children International for its Pippi of Today campaign, helping refugee girls.

"Displaced girls are always the last ones to benefit from any help that comes into a family, so we want to focus on them," Palmberg said. And in the novel coronavirus era, Pippi is more relevant than ever. "Her message is, if you are strong and have power, use it to help others," he explained. "Now more than ever, solidarity is important."

Soon, Pippi fans will have a new film to enjoy, made by Studiocanal, producers of the hugely successful Paddington movies.

"We've had about one offer every week for the last 10 years, but I'm very excited about this," he explained. "We wanted to find a partner that had a track record of taking high-value literary projects, putting them on the big screen, honoring the subject and making something even better. We've been careful but this feels like a match made in heaven."