Development
According to author Angie Sage, the character was in her mind for a long time, and she had already decided what would happen to Septimus in the end but was not exactly sure how she would make the character get there or who he would meet on his journey. For her, Septimus was someone who was in a strange and hostile world and who did not have a clue about who he really was.
Read more about this topic: Septimus Heap (character)