King Vadalon was besieging King Agrippe. If the translation is correct, Vadalon claimed Agrippe had killed Vadalon’s brother, the King of Norgales (North Wales).
Food ran short and all the wells except one supplying the besiegers were dried up. King Agrippe’s daughter poured strong poison into this last well, killing 5.000 besiegers and forcing the others to return to their own country. Vadalon had the princess tracked and seized. Thinking death too lenient, he had two iron bands fixed so tightly round her body that they cut skin in several places.
She defied Vandalon, telling him she would find a deliverer, but would let no one remove the bands unless he also swore to avenge her. Vandalon, she said, would recognize her avenger because he would carry the shield of Vadalon’s brother, whom Agrippe was said to have killed.
The princess, who could travel only in easy stages, was on her way with a few compantions to Arthur’s court to find a champion when Sir Bors found her resting in her pavilion. Swearing to bear the shield in question for a year and a day to punish Vadalon, Bors gently broke her bands with his bare hands.
Source
Vulgate Lancelot | 1215-1230