Missionary in New Zealand, born on 20 April 1814, the son of a Norfolk farmer. He joined the Methodist Church at the age of 17. After two years as a probationer in Ipswich and Horsham he was accepted for missionary service and appointed to Hokianga. He and his wife Sarah sailed with John Bumby, Charles Creed and Samuel Ironside on the James, but on reaching Tasmania early in 1839 he remained there, probably on the instructions of John Waterhouse, the new General Superintendent. The remainder of the year, until a replacement arrived, he spent at Launceston in work among the aboriginal inhabitants, and finally reached his destination in mid-January 1840.
Within a fortnight he was at Waitangi and, though a newcomer, was one of the two WM signatories of the Treaty with the Maoris, signed on February 6. He and Ironside made the journey to keep company with a group of Hokianga chiefs, including Tamati Wake Nene, who was to be influential in his advocacy of the Treaty. Warren's first appointment was to open a new station at Waima, where the notable chief Mohi Tawhai had already built a chapel. He was active in encouraging education for the children of the area, but he also had to contend with the emeregence of the Papahurihia cult. In 1845 his oversight was extended to include Pakanae, a station near the entrance to the Hokianga Harbour, and he made other extensive missionary tours around the whole region.
Warren remained at Waima until 1855, during a period of considerable tension and change. The Northern War of 1846 threatened the stability of the area and his principal task was to encourage his people who were caught up in the conflict. The collapse of the timber trade at that time caused great economic hardship and Warren attempted to establish wheat-growing as an alternative. Education was always a priority for him and he set up adult classes in reading and arithmetic. In 1849 he assisted the repatriation of a large group of former prisoners to their homeland of Taranaki. His oversight covered a large area and he was active in travelling around it.In 1855 he was appointed to Nelson to take responsibility for the English work there. When the Maori communities in Motueka and Wairau sought his help and encouragement, Warren was unhappy that the leaders of the English congregation were so reluctant to release him to do this work. His later appointments were at Wellington (1860-1862), Auckland (1862-1866) and Manukau (1866-1869). He superannuated at the 1869 Conference and lived at Otahuhu in active retirement until his health deteriorated in 1879. He died on 23 November 1883.Warren's ministry was solid and faithful and he was remembered as a skilled and eloquent preacher rather than as a leader and administrator.