The Old English poem Widsith (9th century) refers briefly to his victorious single combat, a story which is related at length by the 12th-century Danish historians Saxo and Svend Aggesen. Offa is also mentioned in the Annales Ryenses, Vita Offae Primi and Vitae duorum Offarum. According to Widsith and the Danish sources Offa successfully conquered the Myrgings, possibly a clan of Saxon origin, and incorporated their land into Angel or Danish lands, by slaying two Myrging princes in single combat and installing himself as their king.