This attack led in turn to the suspension of the king's powers by the Legislative Assembly and the proclamation of the First French Republic on 21 September. In November, proof of Louis XVI's secret dealings with the deceased revolutionary politician, Mirabeau, and of his counterrevolutionary intrigues with foreigners was found in a secret iron chest, the "armoire de fer", in the Tuileries. It was now no longer possible to pretend that the reforms of the French Revolution had been made with the free consent of the king. Some Republicans called for his deposition, others for his trial for alleged treason and intended defection to the enemies of the French Nation. On 3 December, it was decided that Louis XVI, who together with his family had been imprisoned since August, should be brought to trial for treason. He appeared twice, on 11 and 23 December, before the National Convention.