An army of Viking pirates that had besieged the English city of Canterbury for weeks took Archbishop Ælfheah prisoner and seized power.

The siege of Canterbury was a major Viking raid on the city of Canterbury that occurred between 8 and 29 September 1011, fought between a Viking army led by Thorkell the Tall and the Anglo-Saxon defenders. The details of the siege are largely unknown, and most of the known events were recorded in the Anglo-Saxon Chronicle.

Ælfheah, more commonly known today as Alphege, was an Anglo-Saxon Bishop of Winchester, later Archbishop of Canterbury. He became an anchorite before being elected abbot of Bath Abbey. His reputation for piety and sanctity led to his promotion to the episcopate and, eventually, to his becoming archbishop. Ælfheah furthered the cult of Dunstan and also encouraged learning. He was captured by Viking raiders in 1011 during the siege of Canterbury and killed by them the following year after refusing to allow himself to be ransomed. Ælfheah was canonised as a saint in 1078. Thomas Becket, a later Archbishop of Canterbury, prayed to Ælfheah just before his murder in Canterbury Cathedral in 1170.