The Welsh ruler Hywel Dda (Hywel the Good) merges Dyfed and Seisyllwg, establishing a new kingdom known as Deheubarth.
Citation:
Editors. "Welsh kingdom of Deheubarth".
The Literary Encyclopedia. First published 01 May 2009
[http://www.litencyc.com/php/stopics.php?rec=true&UID=7026, accessed 24 May 2013.]