Alba
The ruler of Alba was King Malcolm II (Malcolm the Destroyer), who had ruled since 1005 and would continue to do so until 1034.
Gwynedd
The ruler of Gwynedd was King Llywelyn ap Seisyll, who had ruled since 1018 and would continue to do so until 1023.
Moray
The ruler of Moray at the beginning of 1020 was Mormaer Findláech mac Ruaidrí, who had ruled since 1000. This year, Mormaer Máel Coluim mac Maíl Brigti would take over.
North Sea Empire
The ruler of North Sea Empire was King Cnut (Cnut the Great), who had ruled since 1016 and would continue to do so until 1035.
Strathclyde
The ruler of Strathclyde at this time was likely to have been King Malcolm.