In 793 AD, an anguished Alcuin of York wrote to the Higbald, the bishop of Lindisfarne and to Ethelred, King of Northumbria, bemoaning the unexpected attack on the monastery of Lindisfarne by Viking raiders, claiming it was Norwegians sailing directly across the North Sea to Northumbria.
The truth is this was an insurrection from inside the monastery itself. A set of monks had decided that they wished to convert to a version of what would later be considered a proto-Protestant variant and attacked the monastery from inside trying to launch a revolt. It ended in bloody disaster, however the church tried to blame it on the Vikings to withold the radical ideas of these monks from gaining a foothold.