Cyril Tanner is the carriage driver of the London Institute. His brother Thomas held the position until he died, after which he moved from Brighton to replace him. Their family possessed the Sight, allowing them to see the Shadow World, and has been serving Shadowhunters for centuries.
Tessa noted that, though the Tanner brothers were quite alike, they were also quite different; Cyril had a less diffident demeanor, a difference which she compared to how unlike the Lightwood brothers, Gabriel and Gideon, were, wherein one was calmer while the other was more high-strung.
Cyril is said to greatly resemble Thomas, causing distress on the part of some of Thomas' friends when he first arrived at the Institute.