Tūmate Mahuta was born, probably in July 1893, at Waahi pā, near Huntly. He was the third surviving son of Mahuta, the third Māori King, and his wife, Te Marae. His elder brothers were Te Rata, the fourth King, and Taipu, who died in 1924; his younger brothers were Tonga and Te Rauangaanga. Little is known of the childhood of any of Mahuta's children, but they grew up in the shadow of elders who handed on the story of the Tainui and Kīngitanga past in oral teaching and marae oratory. Tūmate attended primary school at Māngere Bridge, completing his time there in 1907, and was at Huntly school from 1907 to 1909. He spent at least some time at Te Aute College, and may also have attended St Stephen's Native Boys’ School in Auckland. Before the First World War a marriage was arranged for him to Te Ātarua (Piri) Hērangi, younger sister of his cousin Te Puea; they had one son, who died young. Unlike his younger brothers, Tūmate was not conscripted for service in the First World War.
In Te Rata's reign Tūmate often represented his brother. One notable occasion was in 1928, when the King refused to appear for the visit of the governor general, Sir Charles Fergusson, to Ngāruawāhia. In the late 1920s he had political ambitions for the Western Māori seat, but was persuaded to defer to Te Tāite Te Tomo, the preferred successor to the sitting member, Māui Pōmare. In the early 1930s, under the influence of Te Puea and Apirana Ngata, he joined with his brothers in various land development schemes.
At the death of Te Rata on 1 October 1933 Tūmate was about 40 years old. His time as a leader of crucial importance to the King movement was just beginning. Ngata considered him an ambitious man, and wondered whether he might cause trouble over the succession, but there is little evidence that Tūmate aspired to the kingship. His nephew, Korokī (Te Rata’s son), was confirmed as the new King. From the first days of the new reign Tūmate, with his brother Tonga and their uncle Haunui Tāwhiao, were the closest influences on the young King, acting as his guardians and mentors. In 1933 and 1934 he was accompanied by his uncles wherever he went.
About 1933 Tūmate took up the leadership of the association called Rangatahi (young people), founded by Pei Te Hurinui Jones. This group sought to negotiate a settlement of the compensation promised for the Waikato confiscation claim, left in abeyance after the report of the Sim commission of 1927. Tūmate’s position was difficult. Not only was the proposed payment of £3,000 per year not satisfactory to all Waikato and King movement people, but there were differences of opinion as to what would constitute proper compensation. The more conservative element would accept nothing less than the restoration of the confiscated land; Tūmate and his fellow rangatahi were prepared to accept a monetary settlement; the government was determined to keep compensation to the absolute minimum.
On 13 September 1935 Tūmate, Pei Te Hurinui and Te Tāite Te Tomo interviewed Prime Minister George Forbes and Minister of Finance Gordon Coates in Wellington. They were offered a lump sum compensation payment of £100,000, to be administered by a trust board. Tūmate wanted the government to explain how it had arrived at such a low figure. He proposed that the government should pay £250,000 in a lump sum, or £7,500 per annum. Coates explained that this was not satisfactory and a memorandum setting out the government's offer was supplied.
Tūmate's counter-offer was already a compromise. Waikato's counsel in the Sim commission, David Smith, had calculated that land worth £358,666 had not been returned or compensated for. This figure had been adopted as the least Waikato would accept. Any annual payment would have had to exceed £10,000.
Even before Tūmate arrived in Wellington a letter of protest was sent to the prime minister by the third kingmaker, Tarapīpipi Taingākawa Tāmehana Te Waharoa. He still adhered to his position – apparently supported at one time by both Tūmate and Haunui Tāwhiao – that as land was taken so land should be returned, and that any money paid by government should be compensation for its wrongdoing in killing people and destroying chattels. He said that if Tūmate came to any agreement which differed from that position he, as Tumuaki of the kingdom of the Māori people, would not agree.
This kind of protest, punctuated by others from various tribal groups who wanted their own representatives at the negotiating table, accompanied every move made by Tūmate over the next three years. On the other hand, he had some powerful and effective support. At different times Haunui Tāwhiao and Te Puea Hērangi wrote to endorse his position as chief negotiator. Meetings were held at Ngāruawāhia or Waahi after each phase, and when Tūmate, usually assisted by Pei Te Hurinui, explained how the negotiations were going, he was again endorsed as chief negotiator.
In October 1935 Tūmate was in Wellington again. An exchange of letters between Tūmate and the prime minister took place on 7 October. Forbes offered £5,000 a year to commence after 1 April 1936, but reserved the right of the government to pay off the total capital sum of £100,000 whenever it wished. Tūmate replied that he was prepared to accept an interim settlement on those terms, as long as it was without prejudice to striving for an ultimate payment of £358,666; he suggested that in the meantime any reference to the capital sum of £100,000 should be omitted from the settlement. Forbes promised to put this to the cabinet, and on 8 October offered to let the government proposal stand, holding over any further discussion of the capital sum until after settlement.
In January 1936 negotiations began with the new Labour government which, on the advice of the Native Department, claimed that no settlement had been reached. Tūmate and Waikato had been under the impression that they had accepted the government's offer, subject to a proviso permitting a future effort to obtain the full £358,666. Tūmate had been confidently expecting the first £5,000 on 1 April 1936. Late in May the government again offered to renew negotiations. Tūmate responded in June, emphasising his difficulties in striving for a settlement that would reflect tribal opinion and at the same time absolve his family from any future criticism that he had failed to obtain the best possible settlement.
Nothing further transpired in 1936, save that efforts were made to get the prime minister, M. J. Savage, to visit Ngāruawāhia. He did so in March 1937. To convince the conservatives of the King movement that their position was untenable, Tūmate presented Savage with a formal, public request for a settlement based on £358,666 or £10,750 a year. Savage responded by declaring that his government would not be less generous than the previous government and promised to set up a tribunal to reach an agreement.
A round-table conference eventually met in Wellington on 15 February 1938. In the interim, Tūmate was assailed by people who wanted the compensation money distributed to individuals or to separate tribes, and, from November 1937, by challenges led by Tarapīpipi and Marae Erueti (Edwards) to the royal family’s choice of negotiators. On the day of the conference, Tarapīpipi sent a telegram saying that he and Korokī did not recognise the authority of the negotiators and that any settlement arrived at would not be accepted.
Tūmate's views were ably presented at the conference by Pei Te Hurinui. Various sums of compensation were debated, but Tūmate still insisted that a proviso leaving open the possibility of future negotiations was essential. Tūmate eventually accepted that the basis of any settlement would be a payment of £5,000 a year, but at the end of the conference several matters still had not been agreed upon.
Not long after his return to Waikato, Tūmate fell ill, worn out by the stress of fighting a battle on two fronts, and depressed by the attempts to use Korokī ’s name against him. He was taken to the round ponga house at Turangawaewae to see out the last of his days with Te Puea and the rest of the family. He died there on 29 April 1938. During his tangihanga, which was the first of a senior member of the royal family to take place at Ngāruawāhia, Te Arawa came to reproach Waikato and the Tumuaki with causing Tūmate’s death. He was buried on Taupiri Mountain on 8 May.
After the loss of the chief negotiator, the Waikato claim process ground to a halt; formal negotiations recommenced only in 1946. The position accepted by Tūmate in 1938, with some adjustment to cover the 10 years from 1936 to 1946, became the eventual settlement. Tūmate's name was used in 1946 by all parties to sanction their acceptance of the settlement. Eventually Tūmate's hope that the matter would be reopened came to fruition, and a further settlement was reached in 1995 with the passing of the Waikato Raupatu Claims Settlement Act.