Alba
The ruler of Alba was King Kenneth I (Kenneth MacAlpin, the Conqueror), who had ruled since 843 and would continue to do so until 858.
Alt Clut
The ruler of Alt Clut during this time was either King Dumnagual map Riderch (Dumnagaul IV) or King Arthgal map Dumnagual, the exact year of the succession is unknown.
East Anglia
The ruler of East Anglia was King Æthelweard, who had ruled since 845 and would continue to do so until 855.
Gwynedd
The ruler of Gwynedd was King Rhodri ap Merfyn (Rhodri the Great), who had ruled since 844 and would continue to do so until 873.
Mercia
The ruler of Mercia was King Burgræd, who had ruled since 842 and would continue to do so until 874.
Northumbria
The ruler of Northumbria was King Osberht, who had ruled since 849 and would continue to do so until 862.
Wessex
The ruler of Wessex was King Æthelwulf, who had ruled since 839 and would continue to do so until 858.