Nettleship was born in Nottingham, the son of Albert Victor Nettleship and Lilian. He studied Chemistry at the University of Leeds in the late 1950s. He joined the Labour Party at that time, and remained an active member for the rest of his life. After leaving university, he taught in Birmingham, where he married and had three children; the marriage later ended in divorce and he remarried in the 1980s. In 1970 he began teaching at Caldicot School in Monmouthshire, Wales, moving to become Head of Science at Wyedean School in Sedbury, Gloucestershire, a few miles away, in 1974. Joanne Rowling began studying at the school in September 1976, and her mother Anne worked as a technician in the Science department from 1978. He was often known as "Stinger" by pupils due to his last name being "Nettleship". This led to the practical joke of telling first years to ask for "Mr Stinger", which ended up with them getting in trouble. Nettleship described himself in hindsight as "a short-tempered chemistry teacher with long hair... gloomy, malodorous laboratory..". He was first questioned about his links to Rowling's character of Snape by journalists, saying: "I was horrified when I first found out. I knew I was a strict teacher but I didn't think I was that bad." Rowling herself stated that Snape was "loosely based on a teacher I myself had". After being initially unhappy about the comparison, Nettleship came to terms with the connection, and wrote a short book, Harry Potter'sChepstow, about Rowling's connections with Chepstow. He also gave talks on the connections that the Chepstow, Wye Valley and Forest of Dean areas had with the Harry Potter books. Nettleship retired in 1997. As well as being an active member of the Labour Party, he was a member of Caerwentcommunity council, serving as its chairman in 1991. He was instrumental in setting up Caerwent Historic Trust, becoming its secretary and researching the history of the area. He died of cancer in 2011, aged 71, after having been diagnosed in 2006. A spokeswoman for J. K. Rowling said that the author was sorry to hear of his death. He was played by Andrew Kavadas in the J.K. Rowling biopicMagic Beyond Words.
