During his illness Frederick William IV’s brother William, Prince of Prussia, deputized for him, always for three-monthly periods which were then renewed. As Frederick William IV’s marriage had remained without issue, William was the heir apparent of the Prussian monarchy as indicated by the ‘Prince of Prussia’ title. Frederick William’s ministers remained in office during that time. But when after a year it became clear that the King’s incapacity was irremediable it was necessary to transform William’s office into a formal regency, which it remained until the King’s death when William became King of Prussia.