This section is from "The American Cyclopaedia", by George Ripley And Charles A. Dana. Also available from Amazon: The New American Cyclopędia. 16 volumes complete..
Blanche Of Bourbon, queen of Castile, born in France about 1338, died in Spain in 1361. She was the daughter of the duke of Bourbon, and at the age of 15 was betrothed to Pedro, king of Castile, afterward called the Cruel. The king consented to the espousal from political considerations, but all his affection was bestowed upon Maria de Padilla. His natural brother Don Federico having been sent to meet the princess at Narbonne, it was pre-tended that the two were engaged in an intrigue; and though the king married Blanche the next day, he did not conceal his repugnance, and speedily left her for the society of his mistress. She then accepted the protection of the king's brothers, who were causing some political disturbance in Castile. The king declared the marriage void and ordered her to be kept prisoner at the Alcazar of Toledo. She escaped from the guards in the city of Toledo, and taking refuge in the cathedral, aroused the sympathy of the people by her cries, her personal beauty, and her helpless condition.
They attempted 'to protect her, but the city was taken by assault, and the queen was sent to the castle of Medina Sidonia, where she died of poison administered to her by order of Pedro. To avenge her wrongs was one of the principal incentives of the men who a few years later engaged in the war against Pedro, and her story formed the subject of many of the Spanish ballads of that and later ages.