The ruler of Alba was King Donald II (Donald the Madman), who had ruled since 889 and would continue to do so until 900.
The ruler of Gwynedd was King Anarawd ap Rhodri, who had ruled since 878 and would continue to do so until 916.
The ruler of Northumbria was King Eadwulf II (Eadwulf of Bamburgh), who had ruled since 895 and would continue to do so until 913.
The ruler of Strathclyde at this time was likely to have been King Dyfnwal.
The ruler of Wessex at the beginning of 899 was King Ælfræd (Alfred the Great), who had ruled since 871. This year, King Eadweard I (Edward the Elder) would take over.