William Mariner was ship's clerk aboard the British privateer and whaler, Port au Prince. Anchored off the Tongan island of Lifuka, in the Ha'apai group, the Port au Prince was seized by the high chief and future king of Tonga, Fīnau ’Ulukālala, on 1 December 1806. Most of the crew were killed in the takeover of the ship, but Fīnau spared Mariner and several colleagues. Fīnau assumed responsibility for Mariner, taking him under his protection and entrusting his care to one of his wives, Mafihape, who taught Mariner the customs, taboos, dress and language of her people. Mariner lived in Tonga until November 1810, predominantly in the northern island group of Vava’u. He wrote an account of his experiences in Tonga which is one of the major sources of information on pre-Christian Tonga.

A copy of a letter to William Mariner from his Tongan adoptive mother, Mafihape, probably written in 1832, and an English translation of it, transcribed on 6 March 1837 in longhand on the end papers of a copy of Mariner's and Martin's, An Account of the Natives of the Tonga Islands in the South Pacific Ocean, 2nd ed. (Edinburgh: Constable and Co., 1827). This copy of the book is inscribed by Mariner to his daughter, Margaret McCulloch, in 1849. The book is now in the possession of Denis McCulloch of Worcestershire, England.