According to the "Anglo-Saxon Chronicles", Viking raiders struck England in 793 and raided Lindisfarne, the monastery that held Saint Cuthbert's relics, killing the monks and capturing the valuables. The raid marked the beginning of the "Viking Age of Invasion". Great but sporadic violence continued on England's northern and eastern shores, with raids continuing on a small scale across coastal England. While the initial raiding groups were small, a great amount of planning is believed to have been involved. The Vikings raided during the winter of 840–841, rather than the usual summer, having waited on an island off Ireland. In 850, they overwintered for the first time in England, on the island of Thanet, Kent. In 854, a raiding party overwintered a second time, at the Isle of Sheppey in the Thames estuary. In 864, they reverted to Thanet for their winter encampment.