In The Lives of Christopher Chant, he is the boot-boy at Chrestomanci Castle. He has quite a bit of magical ability, and a vivid imagination, particularly when it comes to inventing booby-traps.
He has a pet ferret.
He sometimes mans the scoreboard at the Castle vs. village cricket matches.
He seems to get on better with Christopher than most of the adult Castle staff, although it's not clear how much of this is because they're of an age and how much is because he doesn't have to put up with Christopher all the time.
As an adult, he is a major character in The Pinhoe Egg. He has become a specialist in plant-related magic, and is often away on expeditions across the Related Worlds gathering rare specimens.