Sven was a Viking who took part in an attack on Wulnoth's village in Northumbria in 1066. He and several others fought with Wulnoth and his men. When only he and Ulf survived, Ulf wanted to hide in the monastery. Sven called him a coward.
In the monastery, he and Ulf caught the First Doctor and imprisoned him. However, the Doctor tricked Sven and knocked him out. After Sven found Ulf, who had been tied up by the Monk, they captured the Monk, who informed them he was setting up a beacon for their fleet. As they helped him set it up, however, they were surrounded by the Saxons and killed by them. (TV: The Time Meddler)