AUTHOR'S INSPIRATION: Former head of science John Nettleship says JK Rowling used him as the basis for her character Severus Snape.
HANDS ON: Snape, aka actor Alan Rickman, gets to grips with Harry and Ron Weasley in Harry Potter and the Goblet of Fire.
The ex-Wyedean teacher who inspired sinister potions teacher Prof Severus Snape in the Harry Potter books is to reveal some of the secrets of the wizarding world.
Former head of science John Nettleship taught chemistry to millionaire author JK Rowling when she was a pupil at the Sedbury school.
He now revels in his role as the man behind the reviled character.
John claims that just as he inspired the creation of Snape many places in Tutshill, Sedbury and Chepstow correspond with places in the books.
He is giving a talk at Chepstow Drill Hall during which he reveals the real places behind magical locations in the stories including Diagon Alley and the Green Dragon pub.
He said: "As with all authors, their characters and places are devised from the people they knew and the area they are familiar with.
"Joanne grew up here and the people and places she came into contact with are woven into the tapestry of the books."
Rowling lived in Tutshill and was at Wyedean from September 1976 to July 1983, becoming head girl.
Despite reading all seven Harry Potter books John said he had no idea he was the inspiration for Prof Snape until a reporter knocked on his door to tell him.
John said:"I was horrified when I first found out. I knew I was a strict teacher but I didn't think I was that bad."
In recent years John has started to embrace his fictional depiction, who is played by Alan Rickman in the films.
In his younger days John admits he shared the long black hair of his onscreen self. His talk Harry Potter and Chepstow celebrates the re-release of the spin-off books Quidditch Through the Ages and Fantastic Beasts and Where to Find Them . It is on July 11 at 2pm and tickets are £1, children 50p, The Chepstow Bookshop. There is a prize draw for anyone in fancy dress.