|Occupation||Officer, Ankh-Morpork City Watch|
|Residence||the village of Sunink in New Ankh.|
|Books||Men at Arms|
|Cameos||Thud!, Unseen Academicals|
Bluejohn is first encountered in Men at Arms, where he is recruited into the militia by Carrot and Detritus, and then more prominently in The Fifth Elephant, he is the largest troll ever to be in the Ankh-Morpork City Watch. He is, therefore, a very effective riot shield. In Thud!, he has the rank of constable. He reappears in Raising Steam, still with the rank of constable, where he is described as "gentle as a breeze" and incapable of hurting a fly. although the sight of him provokes anyone with a guilty conscience to run the other way for as long and as fast as it needs. Detritus affectionately regards him as "just a big boy". He lives in Sunink, on the outskirts of New Ankh.
He is named after Blue John, a bright blue mineral once mined in Derbyshire, England (the only place it has been found) and is still crafted by jewellers in the region.