While the churches eventually worked out their differences and came to an initial agreement, both Nicholas I of Russia and Napoleon III refused to back down. Nicholas issued an ultimatum that the Orthodox subjects of the Empire be placed under his protection. <answer>Britain</answer> attempted to mediate, and arranged a compromise that Nicholas agreed to. When the Ottomans demanded changes, Nicholas refused and prepared for war. Having obtained promises of support from France and <answer>Britain</answer>, the Ottomans officially declared war on Russia in October 1853.
Who arranged the compromise that Nicholas agreed to?
Britain