became hysterical and screamed repeatedly: "Mon Dieu, mon fils! mon Dieu, mon fils!" The king then started to beat Wilhelmine and would possibly have killed her. Her siblings and ladies-in-waiting intervened. Frederick's accomplice Katte arrived as a prisoner, so the king beat him instead. When Frederick was imprisoned at the fortress in Küstrin, Grumbkow acted as mediator between Frederick and his parents, managing to reconcile them. The imprisonment was followed by continuous conflict between the king and the queen about the marriage of princess Wilhelmine. While the king pressed for a marriage to the Margrave of Schwedt or the Prince of Weissenfels, the queen exchanged secret messages with her daughter and urged her not to accept any other groom than the Prince of Wales. This conflict caused the king to threaten to beat the queen and have Mademoiselle Sonsfeld publicly whipped. Finally, Wilhelmine was formally offered the choice between the Margrave of Schwedt, the Duke of Weissenfels, or the Prince of Bayreuth. She chose to marry the latter (as she had not seen him but had seen and disliked the other two), on condition that her father free her brother. Her decision was made against the will of her mother, who threatened to disown her for what she considered to be her daughter's lack of courage, and ordered her not to speak to her future groom when he arrived. The king was furious at the cold demeanor of the queen during the following visit of the Prince of Bayreuth. After the betrothal of Wilhelmine and the Prince of Bayreuth, a message arrived in which George II consented to Wilhelmine marrying the Prince of Wales without her brother marrying his daughter Amelia. This message convinced the queen that a Prussian-British marriage alliance was possible. She therefore made a point of harassing the Prince of Bayreuth to stop the wedding. On the day of the wedding (20 November 1731), Sophia Dorothea tried to delay the ceremony by disarranging her daughter's hair every time it had been dressed, saying she was not satisfied with the effect, in the hope that a British courier might arrive in time to stop the ceremony. When Frederick was liberated after his sister's wedding, Sophia Dorothea resumed negotiations with Great Britain to marry him to Princess Amelia, and her next daughter, Philippine Charlotte, to the Prince of Wales, which would complete her life project of a Prussian-British marriage