Who is the famous british author that said to be best selling in history of childrens litreture?

The most widely-read and best-selling children's author of all time is J.K. Rowling, author of the Harry Potter series.

While there are other incredibly popular British children's authors, like Roald Dahl and Beatrix Potter, Rowling's Harry Potter series has sold over 500 million copies worldwide, making it the best-selling book series ever.