Complex sentence: The largest settlements were Ikot Itunko, Obutong and Iboku Atapka, which the British renamed in the 19th century to Creek Town, Old Town and Duke Town.
Split into simpler sentences: The largest settlements were Ikot Itunko, Obutong and Iboku Atapka. In the 19th century, the British renamed these as Creek Town, Old Town and Duke Town.