In Beowulf too we hear of Offa as a mighty king, "the best of all mankind betwixt the seas." But, although his wars are referred to, we are given no details of them. The episode in Beowulf relates rather to his wife Thryth, and his dealings with her. The passage is the most obscure in the whole poem, but this at least is clear: Thryth had an evil reputation for cruelty and murder: she wedded Offa, and he put a stop to her evil deeds: she became to him a good and loyal wife.
Now in the Lives of the two Offas quite a long space is devoted to the matrimonial entanglements of both kings. Concerning Offa I, a tale is told of how he succoured a daughter of the king of York, who had been turned adrift by her father; how when his years were advancing his subjects pressed him to marry: and how his mind went back to the damsel whom he had saved, and he chose her for his wife. Whilst the king was absent on his wars, a messenger whom he had sent with a letter to report his victories passed through York, where the wicked father of Offa's queen lived. A false letter was substituted, commanding that the queen and her children should be mutilated and left to die in the woods, because she was a witch and had brought defeat upon the king's arms. The order was carried out, but a hermit rescued and healed the queen and her children, and ultimately united them to the king.
This is a popular folk-tale which is scattered all over Europe, and which has many times been clothed in literary form: in France in the romance of the Manekine, in English in the metrical romance of Emaré, and in Chaucer's Man of Lawes Tale. From the name of the heroine in the last of these versions, the tale is often known as the Constance-story. But it is clear that this tale is not identical with the obscure story of the wife of Offa, which is indicated in Beowulf.
When, however, we turn to the Life of Offa II, we do find a very close parallel to the Thryth story.
From MS Cotton Nero D. I, fol. 11a
This tells how in the days of Charles the Great a certain beautiful but wicked girl, related to that king, was condemned to death on account of her crimes, but, from respect for her birth, was exposed instead in a boat without sails or tackle, and driven ashore on the coast of King Offa's land. Drida, as she said her name was, deceived the king by a tale of injured innocence, and he committed her to the safe keeping of his mother, the Countess Marcellina. Later, Offa fell in love with Drida, and married her, after which she became known as Quendrida. But Drida continued her evil courses and compassed the death of St Æthelbert, the vassal king of East Anglia. In the end she was murdered by robbers—a just punishment for her crimes—and her widowed husband built the Abbey of St Albans as a thank-offering for her death.
The parallel here is too striking to be denied: for Drida is but another way of spelling Thryth, and the character of the murderous queen is the same in both stories. There are, however, striking differences: for whereas Thryth ceases from her evil deeds and becomes a model wife to Offa, Drida continues on her course of crime, and is cut off by violence in the midst of her evil career. How are we to account for the parallels and for the discrepancies?
As a matter of historical fact, the wife of Offa, king of Mercia, was named (not indeed Cwœnthryth, which is the form which should correspond to Quendrida, but) Cynethryth. The most obvious and facile way of accounting for the likeness between what we are told in Beowulf of the queen of Offa I, and what we are elsewhere told of the queen of Offa II, is to suppose that Thryth in Beowulf is a mere fiction evolved from the historic Cynethryth, wife of Offa II, and by poetic licence represented as the wife of his ancestor, Offa I. It was in this way she was explained by Professor Earle: