Having failed to gain the backing of a European state power to place Radama on the throne and bring the treaty into effect, Lambert decided to instigate a "coup d'état" independently. He traveled to Ranavalona's court in May 1857 in the company of the celebrated 19th-century Austrian globetrotter Ida Pfeiffer, who became an unwitting participant in the plot. She documented her perspective on these events in one of her late works. According to Pfeiffer, Radama and Lambert had planned to dethrone the queen on June 20, when ministers and soldiers loyal to Radama would infiltrate the Rova grounds and declare loyalty to the prince and support for a political transition. Pfeiffer blamed the failure of the plot on Rainilaiarivony, then Commander-in-Chief of the army who reportedly had been unable to ensure the presence of soldiers in the courtyard who were loyal to Radama. According to a British account, however, Radama himself was credited with warning the queen of the plot, in which his cooperation was merely a ploy to entrap the conspirators. The account claimed that Ranavalona deliberately allowed the plot to unfold almost to its conclusion in order to ascertain the loyalties of her members of government. After the plot's discovery, the Europeans were largely confined to their houses on the palace grounds and prohibited from receiving visitors, until an order was issued to immediately and permanently quit the queen's territory in late July.