Article: Russia, as a member of the Holy Alliance, had operated as the "police of Europe", maintaining the balance of power that had been established in the Treaty of Vienna in 1815. Russia had assisted Austria's efforts in suppressing the Hungarian Revolution of 1848, and expected gratitude; it wanted a free hand in settling its problems with the Ottoman Empire — the "sick man of Europe". The United Kingdom could not tolerate Russian dominance of Ottoman affairs, as that would challenge the British domination of the eastern Mediterranean.

Question: Who operated as the "police of Europe"?
Russia