Oswy, after this unexpected victory, now overran Mercia, and subjected it to his sway. His daughter Alchfleda he also gave in marriage to Peada, the son of Penda, and installed him in his father's kingdom, on condition that he should introduce Christianity into his dominions. Alfred, the son of Oswy, in return married the daughter of Penda, whose name was Cyneburga. Thus on each side a pagan was united to a Christian, and the work of conversion went on prosperously; for there were now but few corners of the British dominions in which the true faith was not introduced. Such changes were enough to make the stern old Saxon heathen leap out of his grave. In his lifetime no one would have been found bold enough to have proposed them. Alchfleda's mother was still living, and remained a firm follower of the old idolatrous creed; she seems to have accompanied her daughter into Mercia, and had doubtless in her train many a grey old veteran, who still bowed the knee before the altars of Odin, and who looked upon a religion which taught peace, good will, and charity to all mankind, with disdain. It is not clearly made out by whose instigation Peada was assassinated. Both his wife and her mother stand accused of the deed, but no cause is assigned for the former perpetrating so dreadful a crime; nor can any other reason be assigned for the latter having done it, beyond what we have given. Peada, however, fell at the holy time of Easter, which seems to have been a favourite season for assassination amongst the pagan Saxons, in proof of which numerous instances might be quoted. Before his death, Peada commenced the famous monastery of Peterborough, which his brother Wulfhere completed. Nor was Wulfhere content with only finishing the minster, for he gave to the Abbot Saxulf, to the monks, and their successors for ever, all the lands and waters, meads, fens, and weirs, which lay for many miles around it, and covered in extent what forms more than one English shire. Wulfhere, like Sigebert, appears to have been as much of a monk as a warrior, though a little of old Penda's blood still flowed in his veins; and when Cenwalch, of Wessex, who had been humbled and disgraced by Penda, resolved to have his revenge upon the son, although he was at first successful, the Mercians at last became conquerors, and Cenwalch was again exiled, and his kingdom fell into the hands of the Mercian sovereign.