All through their contest with the Regent, the Protestant leaders took up the position that they were acting in strict accordance with the law of the land. With the formidable following now at their back, they might have marched on Stirling and gained a temporary advantage by their show of strength. What they actually did was to send Erskine of Dun to the Regent to lay their demands once more before her. As she was not yet in a position to enforce her will, she again agreed to postpone action against the preachers. It was the misfortune of her position from the beginning of the struggle that Mary of Lorraine was driven to subterfuges which made impossible any permanent understanding with her discontented subjects; and it was of evil omen for the success of her policy that she now allowed herself to commit a serious breach of faith. In the teeth of her promise to Erskine, she proclaimed the preachers as outlaws when they failed to appear at Stirling on the day appointed for their trial. The news of the Regent's breach of faith was the immediate occasion of the first stroke in the Scottish Reformation. The day after the outlawry John Knox preached a sermon in the parish church of Perth, his theme being the idolatries of Rome, and the duty of Christian men to put an end to them. At the close of the sermon, when the majority of the audience had left the church, a priest proceeded to celebrate mass. A forward boy made a protesting remark; the priest struck him; the boy retaliated by throwing a stone which broke an image, and immediately the church was in an uproar. In a few moments not "a monument of idolatry" was left in the building. The news of these doings spread through the town, and the "rascal multitude" took up the work. There had been old quarrels between the town and the religious orders; and so early as 1543 a violent assault had been made on the Blackfriars' monastery. But on the present occasion the work done was at once more extensive and more thorough. The main onslaught was directed toward the monasteries of the Dominicans and the Franciscans and the Charterhouse Abbey; and within two days, says Knox, "the walls only did remain of these great edifications."