It may be that Ulfcytel was married to a daughter of King Æthelred (by his first wife) named Wulfhild, as suggested by a supplementary text to the Jómsvíkinga saga.
In 1004 the Anglo-Saxon Chronicle reports a bloody battle between the East Anglians and an army led by Danish king Swein Forkbeard.
Two of the Chronicle manuscripts state that the Danes later "admitted that they had never met with harder hand-play [fighting] in England than Ulfcytel gave them".
On this occasion the Battle of Ringmere against the Danes near Ipswich in 1010 turned into a rout, caused by the flight of Thurcytel "Mare's head", and only the men of Cambridgeshire stood to fight.
Alternatively, and less plausibly, Saint Olaf's Saga states that Ulfcytel was killed by Eiríkr Hákonarson near London.