In the year 866 Lo brok's sons Ingwaere (I'varr, q.v.), Healfdene, Ubba and others brought a vast army to England to avenge the death of their father.
In the winter of 874-875 Healfdene returned to Northumbria, which he partitioned among his followers.
In Beowulf we hear of a Danish king Healfdene, who had three sons, Heorogar, Hrothgar and Halga.
Beowulf himself won fame in this campaign, and by the aid of this definite chronological datum we can place the reign of Healfdene in the last half of the 5th century, and that of Hrothgar's nephew Hrothwulf, son of Halga, about the middle of the 6th century.
The exact chronology and relationship of these kings it is impossible to determine, but we know that Healfdene died in Scotland in 877, while Godefridus was treacherously slain by Henry of Saxony in 885.
The Danish king Hrothgar and his brother Halga, the sons of Healfdene, appear in the Historia Danica of Saxo as Roe (the founder of Roskilde) and Helgo, the sons of Haldanus.