He and Sarah sailed on the brig General Gates to New Zealand on 27 July 1819, accompanying Samuel Marsden on his second visit to New Zealand. In 1823, Marsden sailed on the Brampton on his fourth visit, bringing with him Henry Williams and his wife Marianne as well as Richard Davis and William Fairburn, and their respective families. In October 1833 he went with John Alexander Wilson, James Preece and John Morgan to establish a mission station at Puriri on the Waihou River. In 1835, Te Waharoa, the leader of the Ngāti Hauāiwi of the Matamata region, lead his warriors against neighbouring tribes to avenge the death of a relative, with the fighting, which continued into 1836, extended from Rotorua to Tauranga. After a house at the Rotorua mission was ransacked, both the Rotorua mission and the Matamata mission was not considered to be safe and the wives of the missionaries were escorted to Puriri and Tauranga. Fairburn and the other CMS missionaries attempted to bring peace to the belligerents. In late March 1836, a war party lead by Te Waharoa arrived at Tauranga and the missionary families boarded the Columbine as a safety precaution on 31 March. In 1840 he was at the mission station at Maraetai, and was at the Puriri Mission in 1842.
The "Fairburn purchase"
Between 1836 and 1839 Fairburn began moves to establish a mission station at Maraetai while attempting to purchase a vast tract of land from various iwi of Auckland. Brokered as "an act of Christian peacemaking" between warring tribes on the Auckland isthmus, Fairburn obtained "signatures" to the deed of purchase from over 30 rangatira ; few, if any of whom could read or write. Fairburn originally estimated the total area to contain, but it was later surveyed as being around 83,000. When the purchase came under scrutiny from the CMS, in 1837 Fairburn signed a deed promising to return one third of the land to the original inhabitants, and unsuccessfully attempted to offer another third to the Church. Following the 1840 Treaty of Waitangi which established British sovereignty over New Zealand, Fairburn came under investigation from the new government's Land Claims Commission. Following a protracted investigation, in 1848 the Commission disallowed Fairburn's original claim, awarding him instead a much smaller grant of just under. The remainder of the land, including Otara, was retained by the Crown as "surplus land" to be onsold to European settlers. Following the protests of Hori Te Whetuki on behalf of Ngāi Tai, in 1854 the Commission granted a "Native Reservation" of just over at Duders Beach to "the chiefs of the Ngatitai" and paid them £500 compensation, on the condition that they sign an agreement to vacate all other lands within the original purchase boundaries, and order all other iwi to do the same.
