By a law of 1879, the Duchy of Brunswick established a temporary council of regency to take over at the Duke's death. If Ernest Augustus–who had been created the Duke of Cumberland in the British peerage–were unable to succeed, the council would also be empowered to appoint a regent. With William's death in 1884, the Wolfenbüttel line came to an end. The Duke of Cumberland then proclaimed himself Ernest Augustus, Duke of Brunswick. However, since he still claimed to be the rightful King of Hanover, the Federal Council ruled that he would violate the peace of the German Empire if he succeeded to Brunswick. Lengthy negotiations ensued, but were never resolved.