The Mr Men franchise is 40 years old this week - and still sells a copy every 27 seconds.

The creator, Roger Hargreaves, died in 1988 yet he remains the third most successful author of the last decade behind JK Rowling and Dan Brown.

Over the last ten years his books, which include both the Mr Men and Little Miss series, have sold over 11,600,000 copies.

Hargreaves started writing the series in 1971 when his six-year-old son Adam asked him what a tickle looked like.

Adam took over the business from his dad following his death. He said his dad would be amazed that the idea turned into a global brand and lasted so long.

"I think he originally saw them as individual characters and stories rather than being part of a whole series.

"So I think the whole idea of Mr. Men and evolving into a brand was something that wasn't there at the beginning. They were just one-off stories."

The one-off stories have now been translated into 15 languages and Adam adds that he thinks their success is down to the simplicity of the characters and the tales.

"They are wonderful and simple and that's what my dad was striving for.

"Even the shape and the size of the books were designed so that a child could hold them.

"My dad took essentially parts of beings and created the characters - that's why everyone recognises parts of themselves in them."

In 2008 the family sold the rights to the Mr. Men series to entertainment group Chorion in a deal worth £28m.

Rick McShane from Waterstone's bookshop told Sky News: "The first thing that's brilliant is that there are two children's authors in the top three.

"Kids' literacy and getting kids to read has become incredibly important over the last few years.

"What you've got with Roger is someone that starts children reading from a young age.

"You have their parents reading to them and then the children use the books themselves in their first steps of reading alone."