Welcome to the Discworld & Pratchett Wiki. Have fun, contribute and be warned articles may contain nuts and spoilers to the plots of the books.

From Discworld & Pratchett Wiki

Largest troll ever to be in the Ankh-Morpork City Watch, Bluejohn is a very effective riot shield. He is named after Blue John, a bright blue mineral once mined in Derbyshire, England.