Question: Cearl is the first Mercian king mentioned by which English monk at the monastery of St. Peter and its companion monastery of St. Paul in the Kingdom of Northumbria of the Angles?
Sentence (from "St. Peter's Church, Mainz"): Originally it was a collegiate church monastery of ″St. Peter before the walls″, which had existed since the 10th century and is dedicated to the apostle Peter as patron.
Relevant evidence: No