Though the Queen Regent, Mary of Guise, made no move against Knox, his activities caused concern among the church authorities. The bishops of Scotland viewed him as a threat to their authority and summoned him to appear in Edinburgh on 15 May 1556. He was accompanied to the trial by so many influential persons that the bishops decided to call the hearing off. Knox was now free to preach openly in Edinburgh. William Keith, the Earl Marischal, was impressed and urged Knox to write to the Queen Regent. Knox's unusually respectful letter urged her to support the Reformation and overthrow the church hierarchy. Queen Mary took the letter as a joke and ignored it.