943. Edmund stands sponsor to King Olaf, and much later to King Ragnall
The Anglo-Saxon Chronicle states that Edmund stood sponsor to King Olaf at baptism, and then much later the same year to King Ragnall at confirmation. The next annal calls Ragnall a son of Guthfrith, and if he is the brother of Olaf Guthfrithsson he was presumably claiming to be king of York: contemporary coins of York in Ragnall's name support this claim (see Grierson and Blackburn, p.324, which also mentions an otherwise unknown king Sihtric striking coins at York in this period). It is uncertain how King Ragnall's reign related to King Olaf's, though Simeon of Durham's 12th-century note that the Northumbrians drove out Olaf in 943 may suggest that Ragnall took over for 943-4. Since Olaf was still in Northumbria to be driven out by Edmund in 944, it may be that the two kings were fighting over the leadership when the English invaded, much as the (English) Northumbrians had done when faced with Viking attack in 866.
P. Grierson and M. Blackburn, Medieval European Coinage, 1: The Early Middle Ages (5th-10th centuries) (Cambridge: 1986)