Nunn is relatively tall compared to the other staff at Elmsmere. He has facial hair in Series 3, though this disappears in later series. He gels down his ginger hair.
Nunn is shown to be very fond of his physical appearance, describing his own features as "chiselled".
Nunn first appears in Series 3, Episode 3 - Merger. He quickly makes an enemy out of Dexter, who he remains foes with until Dexter leaves Elmsmere. From his first appearance, he's portrayed as egotistical, irritable, and is shown to dislike the children at Elmsmere.
After Isaac becomes the school caretaker, Nunn regularly picks fights with him, similar to how he picks fights with Dexter. Despite the fact that his enemies typically end up on top, his ego remains unscathed.
Crispin Bell becomes another target of his harassment after he becomes headteacher of Elmsmere. This rivalry also extends to Bell's son, CJ, too - Nunn purposefully attempts to get CJ into trouble in a number of plots.
It is shown in Series 7 that he sometimes teaches maths too - it is unknown whether this is a temporary or permanent arrangement.
- In the rap Son of a Nunn, he discusses the prospect of having a child and how he'd be a great father. However, just 4 episodes later, he states that "The last thing [he'd] want is [a child] at home".