Hamilton, Sir Robert George Crookshank (1836–95), public servant, was born in Bressay, Shetland Islands, Scotland, son of Zachary Macaulay Hamilton (d. 1876), minister of the Church of Scotland, and his first wife, Anne (née Crookshank). He graduated MA (March 1854) from King's College, Aberdeen. In 1855 he was recruited as temporary clerk at the war office, London. Serving in the commissariat department in the Crimea during late 1855 and early 1856, he was transferred to the office of works on his return to England. During the 1860s he showed great capacity in taking financial control, first of the department of education (1861–9) and then of the board of trade (1869–78), as government business escalated in complexity and cost. Seconded to the Playfair commission in 1874, he was asked to report on the scope for administrative reform in Dublin Castle and spent some time in Ireland. Made accountant general of the Royal Navy in 1878, he refurbished financial procedure in the admiralty and clarified the presentation of annual naval estimates for the benefit of parliament.
In mid May 1882, days after being made permanent secretary of the admiralty, he was invited, probably by his cousin, George Otto Trevelyan (qv), the newly appointed chief secretary for Ireland, to go as under-secretary into a Dublin administration still in shock after the Phoenix Park murders. For the first year of his tenure he remained on loan from the admiralty. By May 1883 he had warmed to Dublin and Ireland, despite the punishing nature of the job, and accepted appointment as permanent under-secretary at the Castle. Though he had made his name by virtue of his financial authority, he was a broadminded and perceptive administrator with a wide view of his remit. In late May 1883 Hamilton argued for increased expenditure on improvements in Ireland in a memorandum printed for cabinet; later that year he was at odds with his colleague E. G. Jenkinson (qv) on the handling of the nationalist ‘invasion of Ulster’. He was awarded a KCB in 1884. Valued by liberal and conservative viceroys alike, he played an important part in the rejection of Joseph Chamberlain's ‘central board’ scheme of devolution by the Castle executive in May 1885, and its consequent defeat in cabinet. Taking Hamilton's advice that conciliation would best pacify the country, the lord lieutenant, Henry Herbert, 4th earl of Carnarvon (qv), dissuaded the tory administration from renewing the coercive crimes act in June 1885.
It is clear that Hamilton was by this time convinced of the necessity for Irish home rule. Though he never got many in the Castle round to his point of view, he had the tact and administrative authority to thaw tory attitudes even on this issue. In a memorandum to Carnarvon (21 October 1885) he enlarged on the case for home rule, elaborating on a projected two-tier home parliament short only of power over judicial appointments, the army, and the police. Contending that such a concession was no longer a matter of ‘never’ but of when and how, he urged the priority of the ‘Irish question as of the first and supremest importance’ (Hammond, 436). His points took effect, and the memo was circulated among members of government and high-ranking members of the opposition. Gladstone misinterpreted interest in the memo to indicate more widespread support for the proposal in the tory party than was the case; it certainly emboldened him in developing his own home rule initiative. It is not clear how greatly Gladstone was indebted to the specifics of Hamilton's plan for the shape of the Liberal home rule bill of 1886. It seems, however, that he followed Hamilton's advice to get the land question settled by assisted tenant land-purchase before attempting to introduce home rule.
In spring 1886 Hamilton had a tussle with the Irish lord chancellor over an attempt to restrict the salary of the attorney general to £4,000. On the resumption of tory government in July 1886, there were vigorous calls among Irish unionists and in The Times for his removal. Claiming that his presence in the Castle undermined police morale, the 2nd duke of Abercorn (qv) declared Hamilton was ‘the fons et origo of nearly all the mischief that has been instilled into the late prime minister's infantile brain’ (Curtis, 130). Sir Michael Hicks Beach (qv), as chief secretary (1886–7), thought him too good an administrator to lose, but the campaign finally bore fruit in November 1886 when Hamilton was appointed governor of Tasmania (at a salary of £5,000; Beach got him the post). He returned to London in 1893, first to work on two royal commissions of inquiry, then to take chairmanship of the board of customs. He died 22 April 1895 at his residence 31 Redcliffe Square, South Kensington, and is buried at Richmond, Surrey.
He married first (1863) Caroline (d. 1875), daughter of Frederick Augustus Geary (d. 1845), and second (1877) Teresa Felicia, daughter of Maj. H. Reynolds of the 58th Regiment. Both marriages produced children.