According to family information, Robert Henry Wynyard was born on 24 December 1802, at Windsor Castle, Berkshire, England; he was baptised in London on 13 February 1803. He was the younger son of Jane Gladwin, lady-in-waiting to Queen Charlotte, and her husband, William Wynyard, colonel of the 5th Regiment of Foot, deputy adjutant general, and equerry to George III. After attending a school in Dunmow, Essex, Robert Wynyard followed family tradition in choosing a military career. In February 1819 he was appointed ensign in the 85th (Duke of York's Own Light Infantry) Regiment and in 1826 was transferred to the 58th (Rutlandshire) Regiment of Foot. Although he served for some years in England, it was in Malta, on 12 August 1826, that he married Anne Catherine McDonell, daughter of Hugh McDonell, the British consul general at Algiers. They were to have four sons.
From 1828 to 1841 Robert Wynyard served in Ireland on the staff of the adjutant general, and was promoted to major in 1841. Recalled to England in 1842, he was appointed to command the 58th Regiment and promoted to lieutenant colonel. In 1844 the regiment was posted to Sydney, Australia. Shortly after their arrival, however, Wynyard, with 200 troops, was ordered to New Zealand to augment the forces deployed in the Bay of Islands against Hōne Heke and Kawiti. Wynyard was one of the party who stormed Ruapekapeka on 11 January 1846. In recognition of his services in the northern war he was created CB.
In December 1846 the Wynyards returned to New South Wales, but Robert Wynyard was again posted to New Zealand in 1847. Over the next 11 years they entertained lavishly in their home at Official Bay, Auckland. This period is documented in a series of watercolours and drawings executed by Wynyard. In 1851 he was appointed, on the death of Major General G. D. Pitt, to command the forces in New Zealand, amounting to some 1,000 imperial troops and the 500 Fencibles in the Auckland pensioner settlements. He held this command until 1858, being promoted to colonel in 1854. From April 1851 to March 1853 Wynyard held the position of lieutenant governor of New Ulster, to which he was appointed by Governor George Grey. Grey gave him only limited powers, but in this capacity he inaugurated the first municipal corporation, in Auckland. Aided by Bishop George Selwyn and Chief Justice William Martin, he also successfully obtained consent from Ngāti Tamaterā and Ngāti Raupunga to goldmining in the Coromandel area, and later the Thames, Karangahake, Waihī and Te Aroha fields. The subsequent exploitation of these goldfields was to have major consequences for the economic development of Auckland province.
In 1853, when Grey proceeded to implement the provincial government provisions of the 1852 constitution, Wynyard was persuaded to stand for the office of superintendent of Auckland province. Despite refusing to canvass for votes, he won the election after a bitter contest between the Auckland Constitutional Association, which had nominated him, and the supporters of the Progress Party, who called for representative government and cheap land. His success was in large part due to the support of the military pensioners and government servants and appointees in the province.
When Grey departed for England at the end of 1853, Wynyard, as the senior military officer in the colony, became acting governor, assuming office on 3 January 1854. For 12 months he held both elective office and the acting governorship in addition to his army appointments. This aggregation of power gave fresh ammunition to those opposed to the rule of autocratic governors responsible only to Whitehall. Eventually, in January 1855, Wynyard resigned the superintendency following instruction from the secretary of state for the colonies, George Grey.
In spite of his earlier lack of confidence in Wynyard's political expertise, Governor Grey had left to his stand-in the daunting task of completing the implementation of the New Zealand Constitution Act 1852. This involved inaugurating the first New Zealand parliament, and defining the respective powers of the provincial and central governments. Wynyard had the aid of the Executive Council, including the attorney general, William Swainson, the colonial treasurer, Alexander Shepherd, and the colonial secretary, Andrew Sinclair. He was also advised unofficially by Edward Gibbon Wakefield, MHR for Hutt, until the House forbade this. When he addressed the first General Assembly in the hastily erected parliament building in Auckland on 27 May 1854, Wynyard emphasised that his powers were circumscribed and his responsibility was to the Crown. The Assembly proceeded to pass a resolution proposed by Wakefield calling for responsible government. On the advice of Swainson, and with the concurrence of the rest of the Executive Council, whose appointments would cease if this were acceded to, Wynyard declared that he had no power to do so. James Edward FitzGerald, MHR for Lyttelton, and Henry Sewell, MHR for Christchurch, however, argued that there were no legal obstacles to such a step. This view was later confirmed by the secretary of state for the colonies.
There ensued a period in which government was carried on by the old executive in the face of opposition from the newly elected members. Wynyard made various attempts to solve this impasse, including appointing four elected members to the executive. However, prevented by the existing incumbents from exercising power, they resigned. Eventually, he obtained approval for the introduction of responsible government and authority for pensioning off the senior officials who formed the old Executive Council. The new General Assembly met on 8 August 1855.
The delay in calling the General Assembly, and the failure to introduce responsible as well as representative government, resulted in a deadlock that allowed provincial interests to become entrenched at the expense of central government. The blame for the confusion which arose appears to lie not so much with Wynyard as with the Colonial Office for omitting mention of responsible government in its instructions. It also lies to some extent with Grey. Calling the General Assembly himself would have meant grasping the nettle of settler opposition to the rule of governors. As an experienced governor, Grey was much better equipped to do this, but instead he left it to an interim administrator, whom he had not trusted with any great freedom of action as lieutenant governor of New Ulster, and had omitted to brief on the niceties of the British constitution. The frustrations of the parliamentarians were vented on Wynyard instead of the distant Grey.
In September 1855 the new governor, Thomas Gore Browne, arrived to take over from Wynyard. After 20 stormy months as acting governor, Wynyard resumed his military duties. In 1858 the 58th Regiment was recalled to England, where Wynyard was promoted to major general. The following year he was sent to South Africa as officer commanding and lieutenant governor of Cape Colony, once again with Grey as governor. Wynyard deputised as governor and high commissioner of Cape Colony from August 1859 to July 1860, and from August 1861 to January 1862. In 1863 he returned with Anne Wynyard to England in ill health. On his retirement he was promoted to lieutenant general and appointed colonel of the 98th Regiment of Foot. He died in London on 6 January 1864. Anne Wynyard returned to Auckland, where she remained a prominent social figure until her death on 2 November 1881.
A competent staff officer, Robert Wynyard was endowed with sound practical sense and average ability. He was a tall, handsome man, with a patrician style and much charm. A later military writer described him as 'undoubtedly the most popular man who ever came to New Zealand'. Henry Sewell, however, was less complimentary: 'He was a weak but well-meaning man who might have done better had he fallen into better hands.' Thrust into the maelstrom of politics, Wynyard was forced to wield executive power at a juncture unique in New Zealand history. However inept and ill advised, he was nevertheless the prime mover in the constitutional changes in the period of transition from colonial to parliamentary government.