The Māori language did not have an indigenous writing system. Missionaries arriving from about 1814 learned to speak Māori, and introduced the Latin alphabet. In 1817, Tītore and his junior relative, Tui, sailed to England. They visited Professor Samuel Lee at Cambridge University and assisted him in the preparation of a grammar and vocabulary of Māori. Thomas Kendall travelled to London with Hongi Hika and Waikato (a lower-ranking Ngāpuhi chief) in 1820, during which time further work was done with Professor Lee, who gave phonetic spellings to a written form of the language, which resulted in a definitive orthography based on Northern usage. By 1830 the Church Missionary Society (CMS) missionaries had revised the orthography for writing the Māori language; for example, "Kiddeekiddee" became, as in the modern spelling, "Kerikeri". Māori distinguishes between long and short vowels; modern written texts usually mark the long vowels with a macron. Some older texts represent long vowels with double letters (for example: rather than ); for modern exceptions see below.