The skilful ambiguity of the subtitle of Geoffrey Lewis’s biography of Carson - The Man Who Divided Ireland - is undercut by its concluding premise: “Ireland was and is two nations and two races. Those, from Gladstone to de Valera, who felt that Ireland must control its own destiny, could never accept that awkward fact”.

This peremptory and over-determined assertion does not do justice to Lewis’s balanced and intelligent account of the career of Edward Carson as a lawyer and politician.

Though Carson was born in Dublin, educated in Portarlington, attended Trinity, was called to the Irish bar in Easter 1877, and practised on the Leinster Circuit, his career thereafter rapidly deviated from the southern unionist norm. It took a decisive political turn in the aftermath of the defeat of Gladstone’s first home rule bill. Carson was appointed crown counsel by Salisbury’s chief secretary, Sir Michael Hicks Beach, and was patronised, in the 18th-century sense, by the lord lieutenant, the sixth Marquess of Londonderry. The transformation of Carson quickened with the appointment of Arthur Balfour as chief secretary in 1887: Carson provided the stern prosecutorial face of Balfourian “coercion”. Balfour formed a shrewd estimate of Carson’s ability and determined not to lose him to judicial preferment. Balfour’s direction of Carson’s career into politics was important for the furtherance of the Salisbury-Balfour anti-nationalist strategy in the longer term, and suggests that the chief secretary felt that, as it stood, Irish unionism was not equal to its historic task of upholding the union against the combination of Parnellite nationalism and Gladstonian Liberalism.

Carson was appointed solicitor general and elected for one of Trinity’s two parliamentary seats in 1892. He continued to represent Trinity for 26 years. He moved to practise at the English bar.

Carson’s career was thenceforth based in England rather than Ireland. It is clear that insofar as he was an Irish unionist member of Parliament he was very much on the right of Irish unionism. From the outset he was strikingly immune to the sensitivities of, and free from sentimental identification with, southern unionism. In a fascinating memorandum to Bonar Law, the newly elected leader of the Conservative party in November 1911, quoted by Lewis, Carson explained why the question of separate treatment for Ulster was not canvassed in the debates on Gladstone’s second home rule bill in 1893: “During the opposition to the Bill in 1893 we frequently discussed this question and Mr Chamberlain I think was always in favour of creating the difficulty for the government, but the Irish members never would agree to it and I don’t think it was ever raised as a substantive amendment.” By “Irish members” he meant Irish unionist members excluding himself. Such was the abstract constitutional rigour of Carson’s unionism that it yielded nothing to the Anglo-Irish sense of terroir.

In the final crisis, or succession of crises, Carson passed through the staging post of believing - or professing to believe - that the mooting of partition would be a safe and effective tactic because Redmond could never accept it, to espousing partition. As Lord Lansdowne memorably concluded, “he means to fight on his inner lines”. Southern unionists never quite forgave Carson, for reasons that were not wholly reducible to a sense of betrayal. With the establishment of the two states the estrangements within unionism as well as within nationalism deepened. Lewis quotes the bizarre comment in the Irish Times obituary on Carson, who died on October 22nd, 1935, the last of the great Irish figures of the home rule drama, that “had he been 40 years younger, Lord Carson of Duncairn might have been a British Hitler or even a Mussolini”.

Carson was bereft of political imagination or reflectiveness. This served him well in his historic role if it makes a somewhat forbidding subject for a political biography. His career was defined by the denial that he was engaged in politics. He saw himself as a patriotic conscript rather than a politician, obliged in a time of peril to forsake his professional life to defend the existing constitutional order. His modus operandi was that of a barrister brutally wresting and imposing a settlement.

Carson’s imposing features belied constant problems of health. The set jawline, and the cavernous eye sockets, provided the stern icon of Ulster unionist resolve skilfully promoted by James Craig. His record as this implacable upholder of the law in Ireland aided him in the essential business of distinguishing loyalist resistance to home rule from the sedition of nationalism. By the same token, what was to nationalists the open admission that the Conservative conception of law and the constitution was and had always been a partisan sham inflamed nationalist resentment of partition and helped seal the fate of the Irish parliamentary party: the final Balfourian barb.

Carson was the predominant Irish unionist figure in the last moment of high politics, and the final agonies of the “Irish question” in the late 19th- and early 20th-century politics of these islands. He never had to practise politics at a lesser altitude. He was never obliged, as was his admirer, inheritor and fellow lawyer David Trimble to address the predicament of governance within the Northern Irish state.

Lewis is incorrect in stating that Carson’s birthplace was demolished. Number 4 Harcourt Street still stands, though with its interior greatly compromised, saved by the efforts on behalf of An Taisce of Ian Lumley, Michael Smith and the splendid and still missed Rico Ross. It even has a plaque.

As if to perpetuate the cycle of miscomprehension, the belated plaque that now adorns the house refers to “Lord Edward Carson”: appointed a lord of appeal in ordinary in 1921, Carson became Lord Carson of Duncairn, after the division of Belfast he had represented from 1918.