Halfdan I Ragnarsson reputed to be one of the sons of Ragnar Lodbrok. He participated in raids in England in 855, then became one of the leaders of the Great Viking Army. He ruled London in 871 and 872, where coins were minted with his image.
In 875, he seized Northumbria and became King of Yorkuntil his death in 877. The Viking kingdom of York then seems to have remained in the hands of Ecgberht II of Northumbria then in those of Eadulf I of Bernicia, it will only regain its independence with the election in 883 of a new Viking king:Gothfrith.