Nigel "Gravedigger" Sykes was the teacher of Anthony Lockwood in becoming an agent. He had a great reputation as a master swordsman.
He took in the young Anthony Lockwood as an agent after hearing of Lockwood's deeds to the ghost that took the life of the boy's sister (Book 3:24). Later, he entered Lockwood in DEPRAC's fencing competition wherein Lockwood bested a much older and more experienced Quill Kipps.
Lockwood referred to him as the "bane of Fittes and Rotwell" for reasons not stated but can only be surmised (told by Anthony Lockwood Book 3:24 ).
He seemed to have died in a horrible manner not specifically stated (told by Flo Bones Book 2:12 ).