Like other native Greek Catholics, they celebrate Easter using the same calendar as the Greek Orthodox church. The Cathedral of St. James and St. Christopher in Corfu City is the see of the Roman Catholic Archdiocese of Corfu, Zakynthos and Cephalonia. The island served also as a refuge for Greek scholars, and in 1732, it became the home of the first academy of modern Greece. A Corfu cleric and scholar, Nikephoros Theotokis (1732–1800) became renowned in Greece as an educator, and in Russia (where he moved later in his life) as an Orthodox archbishop. The island's culture absorbed Venetian influence in a variety of ways; like other Ionian islands (see Cuisine of the Ionian islands), its local cuisine took in such elements and today's Corfiot cooking includes Venetian delicacies and recipes: "Pastitsada", deriving from the Venetian "Pastissada" (Italian: "Spezzatino") and the most popular dish in the island of Corfu, "Sofrito", "Strapatsada", "Savoro", "Bianco" and "Mandolato". 19th century By the 1797 Treaty of Campo Formio, Corfu was ceded to the French, who occupied it for two years as the département of Corcyre, until they were expelled by a joint Russian-Ottoman squadron under Admiral Ushakov. For a short time it became the capital of a self-governing federation of the Heptanesos ("Seven Islands"), under Ottoman suzerainty; in 1807 after the Treaty of Tilsit its faction-ridden government was again replaced by a French administration under governor François-Xavier Donzelot, and in 1809 it was besieged in vain by a British Royal Navy fleet, which had captured all the other Ionian islands. Following the final defeat of Napoleon at the Battle of Waterloo, the Ionian Islands became a protectorate of the United Kingdom by the Treaty of Paris of 5 November 1815 as the United States of the Ionian Islands. Corfu became the seat of the British Lord High Commissioner of the Ionian Islands. The period of British rule led to investment in new roads, an improved water supply system, and the expansion of the Ionian Academy into a university. During this period the Greek language became official. Following a plebiscite the Second National Assembly of the Greeks at Athens elected a new king, Prince Wilhelm (William) of Denmark, who took the name George I and brought with him the Ionian Islands as a coronation gift from Britain. On 29 March 1864, the United Kingdom, Greece, France and Russia signed the Treaty of London, pledging the