Henry John Tancred was baptised on 14 May 1816 at the Isle of Wight. He was the younger son of Sir Thomas Tancred, sixth baronet, and his wife, Harriott Lucy Crewe. The Tancred family had held its lands at Boroughbridge, Yorkshire, England, from Norman times. He was educated at Rugby School, and served in a hussar regiment of the Austrian army, being involved in the suppression of the revolutionary movements of 1848 in Vienna, Pesth and Lombardy. He was severely injured in a fall from a horse, and was handicapped in later life as a consequence.
While in England on sick leave he became interested in the Canterbury Association, resigned his Austrian commission and bought land in the projected settlement. Elected to the councils of both the association and the Society of Canterbury Colonists, he emigrated before the Canterbury Pilgrims, meeting J. R. Godley in Wellington and reaching Lyttelton on the Barbara Gordon in December 1850. When the Society of Canterbury Colonists became the Society of Canterbury Land Purchasers, Tancred was elected to its council, and in 1852 he was made chairman of the Christchurch Colonists' Society. With his elder brother, Sir Thomas, seventh baronet, he took up land; first the Malvern Hills station in 1852 and then the Ashburton station in 1853.
In 1853 Tancred was one of three candidates for the post of provincial superintendent, which J. E. FitzGerald won. Tancred's speech had been permanently impaired as the result of a broken jaw and he was unable to make an election address. His brother, Sir Thomas, who spoke in his place, made inept comments which probably lost votes. However, Tancred was elected to the first provincial council and was chosen by FitzGerald as president of a provisional executive, soon to be replaced by a regularly constituted executive. He was a member of the provincial council until 1857 and again from 1864 to 1876. Further, he served on the provincial executive from 1853 to 1858 and from 1864 to 1866. He was both speaker and deputy superintendent for the decade before abolition in 1876. Yet he was more of an administrator than a politician. He was a director of public companies, consul for Austria in Christchurch, resident magistrate in both Lyttelton and Christchurch, keeper of public records, sheriff and commissioner of police.
Early in 1856 Tancred was called to the Legislative Council, and was member without portfolio of the Bell–Sewell executive which fought the question of responsible government. In 1858 he became a member of the Stafford ministry. He was secretary of Crown lands, then postmaster general, and administered these portfolios until 1861 when the government was defeated. He was again minister without portfolio in the Domett ministry of 1862–63. In Parliament he did not speak often or long. 'His mind, always firm and manly, was perhaps of too judicial and philosophical a temperament to be well adapted to the rude, illogical intemperate scuffle of modern politics.' Retiring from the Legislative Council in 1866, he won the Ashley seat in the House of Representatives in 1867 and served until 1870.
Tancred's major interest was education. He was an elected fellow of Christ's College, and became involved in both administration and teaching. It was the intention of the Canterbury Association to have a collegiate or upper department of its secondary school. In accordance with this plan, Tancred was in 1859 appointed Hulsean–Chichele Professor of Modern History at the school and thereafter he lectured annually on the glories of Byzantium. However, comprehensive tertiary education was not established in Christchurch for another decade.
When the provincial council set up a commission on education in 1863, Tancred became chairman, and subsequently a member of the board of education. The report of the commission, now regarded as of major importance, recommended the establishment of a provincial board of education, with local committees to administer public schools which would gradually replace the existing denominational schools. It was, however, in tertiary education that Tancred's influence was of greatest significance.
In the complex manoeuvring which accompanied the establishment of a national university system, Tancred with William Rolleston and Hugh Carleton played a major role. Otago interests, led by James Macandrew, established a university under an ordinance of the provincial council in 1869, and made progress towards securing colonial and not merely provincial status for the institution. Although Tancred had earlier favoured independent, local, teaching universities, like Otago, he changed his view and became the leading advocate of a colonial university. The New Zealand University Act 1870 established a university which was to incorporate Otago University and be centred in Dunedin. In 1871 Tancred was elected chancellor with Carleton as vice chancellor. The university council then converted its institution into an examining and degree granting body without a permanent site, and with power to affiliate teaching institutions including schools. Tancred remained chancellor of the University of New Zealand until his death in 1884.
In 1871 Canterbury interests founded the Canterbury Collegiate Union, of which Tancred became lecturer in history without fee. The union was dissolved in May 1874. About the same time Canterbury College, founded in 1873, affiliated with the University of New Zealand, which alone granted degrees. Tancred was a member of the board of governors of Canterbury College from 1873 to 1884.
A new University Act in 1874 defined the future course of university education. The legislation was framed in consultation with those involved in university administration. Although Tancred had earlier held the view that examinations did not afford adequate indication of a graduate's attainments, he became the principal author of the system of overseas examiners, which dominated university teaching until 1940. He believed that external examiners were needed to ensure equal justice for students taught in different institutions for a common degree, and to check the quality of teaching. He also held that university teaching should be widely available throughout the country, so that it would not become limited to the wealthier sections of the population.
Tancred's commitment to education was allied with his deep interest in cultural matters. In 1880 he was chairman of the meeting to found the Canterbury Society of Arts, and he became its first president, from 1881 to 1882.
On 30 July 1857 at Nelson Tancred married Georgeanna Janet Grace Richmond. There were no children of the marriage. Tancred died at Christchurch on 27 April 1884. His widow established the Tancred Prizes for History and Literature at Christ's College in his memory.