It’s 873 and so far Halfdan has extracted THREE Danegelds from King Burgred in exchange for promising to not occupy Mercia. And, of course, he’s gone on to occupy Mercia… most recently in a town called Torksey. He also put down a rebellion in Jorvik and reclaimed the city. He pushed King Ricsige of Northumbria beyond the Tyne, effectively demoting him to King Ricsige of Bernicia. And now, he was marching (or potentially rowing) towards Repton, which was also in Mercia.
Burgred couldn’t catch a break with this guy.