Analysis of information sources in references of the Wikipedia article "Horrid Henry" in English language version.
The idea for Horrid Henry came about when an illustrator friend of Francesca Simon's asked her to write a book about a naughty child, as she was fed up of drawing angelic children! As the eldest of four children, Simon also wanted to write about the relationships between brothers and sisters, and so she created Perfect Peter. Although she says she adores Peter, Simon admits that Henry is most people's favourite; he is the "imp inside everyone" and of course it's "sometimes great to let that imp out"!
I get my ideas from things that happen to me, or to people I know, or from my imagination. I think of ordinary situations, like birthday parties or getting nits, and then add a "horrid" twist. So if my son, Josh, has to have an injection, I think of how Henry would behave.