It appears to have been in 1826 that Conner married the widow of an army officer; through this marriage he became a landowner in 1826, residing at Inch (on the Kildare–Laois boundary, near Athy). In an 1842 pamphlet he declared that he received rent in three counties and had property in the Funds (i.e. government loan stock), while his wife received a significant pension; he lost much of his income in 1843 through the termination of a lease based on lives, but retained a comfortable economic position. In one of his pamphlets he referred to his children, but in the present state of research nothing is known about them.
According to Conner himself, he undertook an eighteen months’ tour of Ireland (excepting a few northern counties) on which he talked with all classes of farmers and labourers, and in 1828 (as a result of these travels?) devised the scheme for the settlement of the Irish land question which he preached for the remainder of his life. This was summed up as ‘a valuation and a perpetuity’ – that rents should be fixed by an independent valuer and tenants should be entitled to remain in place as long as they paid this rent; they were also entitled to dispose of their tenant right to a buyer of their choice. In 1830 he subjected his own estate to a valuation by two farmers and set its rents accordingly. In 1835 Conner visited London where (according to himself) he submitted his scheme to the scrutiny of the ‘ablest writers’ on political economy.
Conner's preferred literary genre was the speech, published as a pamphlet with introductory remarks. In 1832 and 1835 he embarked on speaking tours of Leinster and parts of Munster, propounding his theories at after-mass meetings; both tours were curtailed because of agrarian violence connected with the anti-tithe campaign. The first statement of his views was published in 1832 as The speech of William Conner, Esq., against rack-rents, &c; delivered at a meeting at Inch, in the Queen's county, convened for the purpose of taking into consideration the condition of the farming and labouring classes, and for petitioning parliament for a bill for the applotment or valuation of land by a sworn jury. This was republished with a new introduction in 1835 as The true political economy of Ireland; or, Rack-rent the one great cause of all her evils: with its remedy.
His style of oratory is strongly influenced by William Cobbett; he made a point of using plain and direct imagery to bring home to his audiences the advantage offered by his plan, and despite his own landowning background he spoke of society as divided into ‘the industrious class’ and ‘the idle class’. He justified his departure from freedom of contract by arguing (in Lockean terms) that, since the supply of land was limited, the landlords were in the position of monopolists and their contracts with the tenants were not in fact free; he pointed to the corn laws as a precedent for state interference. He claimed to have read widely on political economy, and made use of the marginal utility argument (though he did not use the term) in proposing that a redistribution of income from landlords to tenants would increase the market for Irish produce. Conner believed that his theories were as demonstrable as a mathematical proposition; this certitude, and his tendencies towards egotism and self-dramatisation, brought about an intransigence which limited his political effectiveness (though, given his radicalism by contemporary standards, he was unlikely to receive much support from the political establishment in any case). He was dismissive of possible Malthusian criticisms of his plan, simply refusing to believe that Ireland could not support a numerous population in comfort. Conner also opposed the poor law on the grounds that it encouraged idleness, while his plan would bring about productivity through labour and allow the natural charitable impulses to flourish. In 1840 he published another pamphlet, The axe laid to the root of Irish oppression.
In the early 1840s Conner joined the Repeal Association and embarked on another speaking tour of the country. A speech at Mountmellick in 1842 led to his imprisonment for six months on charges of incitement. It combined reminders of the physical vulnerability of landlords to agrarian violence with O'Connellite condemnations of violence and advocacy of peaceful protest; the prosecutors, however, apparently treated the latter as mere camouflage. Conner subsequently published the speech in a pamphlet (with a lengthy introduction) as The prosecuted speech: delivered at Mountmellick in proposing a petition to parliament in favour of a valuation and a perpetuity of his farm to the tenant: with an introductory address on the nature and spirit of toryism. (The ‘introductory address’ claimed that the tories knew the validity of his theories but failed to act on them through cowardice and self-interest.) The Repeal Association took up the call for ‘fixity of tenure’, but defined this in terms less far-reaching than Conner's. Daniel O'Connell (qv) argued that Conner's scheme went too far in entrenching the landlord's property rights, that it offered nothing to labourers (Conner in fact said that labourers’ wages should be fixed at a fair rate by the same arbitration process used to set rents), and that by stereotyping present ownership patterns it would deprive industrious labourers of any hope of coming to hold land. Conner, who believed that the least departure from his scheme would lead to the reintroduction of rack rent, cannot have been impressed by this; The prosecuted speech combines praise for O'Connell with some sharp remarks on his bias as a landlord.
In 1843 Conner published A letter to the Right Honourable the earl of Devon, chairman of the Land Commission, on the rackrent system, showing its cause, its evils, and its remedy, calling on the commission to take up his proposals; he suggested that the valuation might be made by a state official rather than a jury and suggested Griffith's valuation as a basis. In the same year he moved from his previous advocacy of petitioning parliament to advocacy of a rent strike; he himself refused to pay rent on a holding at Inch and in March 1843 prevented an auction of his goods by summoning a mass meeting for the same time and place. Conner was promptly expelled from the Repeal Association, receiving virtually no support from any of its members. His bitterness at this experience was reflected in an 1846 pamphlet, Two letters to the editor of The Times; though aimed primarily at attributing Irish poverty to rack rents rather than a racially inherited Celtic laziness (as claimed by the London Times reporter – or ‘special commissioner’ – T. C. Foster), this was prefaced by a vitriolic denunciation of all shades of Irish political opinion, including both ‘the nonsensical, bombastical and perfidious Nation’ and O'Connell, whose ‘lawyer-like ambiguity’ is described as having reduced the phrase ‘fixity of tenure’ to such fuzziness that not even the monster telescope of William Parsons (qv), Lord Rosse, could find a meaning in it.
At some point in the early or mid 1830s Conner's associates included James Fintan Lalor (qv). The extent of Conner's influence on Lalor is unclear; it has been suggested that, while Lalor echoed Conner's emphasis on law and his belief in public propaganda based on a few simple principles, he went further than Conner in his famine-era view that the position of the tenants called into question the very basis of political allegiance and that the land question could be solved only by making landowners acknowledge that their rights of property derived from the Irish nation (the basis of the later neo-Fenian belief that the British parliament was too heavily dominated by the landed class to make significant concessions to Irish tenants).
The view of George O'Brien (qv) of Lalor as land nationaliser and Conner as believer in private property is generally recognised as a distortion; Lalor's views on the origin of land title did not mean that he believed in absolute state ownership, while the strong statement by Conner on property rights quoted by O'Brien comes from the 1822 Letter to the people of Ireland, written before his thought had fully developed. Conner and Lalor had separated by 1840, when Lalor was active in a local savings society near his family home in Tinnakill, Queen's Co. (Laois).
In September 1847, when Lalor held a meeting at Holycross, Co. Tipperary, with the intention of forming a tenants’ society, Conner attended and gave a speech listing his own activities on behalf of the tenants and advising them to stick to demanding ‘a valuation and a perpetuity’. Lalor called him an irrelevant ‘spouter’, taking up the meeting's time and coming with the intention of causing trouble; Conner retorted by accusing Lalor's father and Lalor himself of ‘squeezing the last penny from their tenants’, whereas Conner had granted his tenants a valuation. The two men came to blows and the platform collapsed under them; the meeting broke up in disorder, with Conner speaking from the ruined platform while Lalor's supporters chaired him to the nearest pub. Some early twentieth-century separatist writers, ignorant of Conner's career and earlier connection with Lalor, suggested that he had disrupted the meeting as a British agent, rather than from egotism and personality differences; there is no evidence whatsoever for this view.
A catechism of valuation and perpetuity of tenure (3rd ed., 1850) is addressed to ‘Brothers of the Tenant League’, of which Conner claims to be a member; A letter to the tenantry containing an exposition of the rackrent system (1850) expresses suspicion of the nascent league as latecomers and opportunists and contains extracts from a laudatory letter addressed to Conner by John Stuart Mill, who, in Chapters and speeches on the Irish land question, paid tribute to him as ‘the earliest, most enthusiastic and most indefatigable apostle’ of Irish land reform (quoted in O'Brien). Conner was present at the 1851 conference which organised the league on a national basis, but took little further part in its affairs. He published nothing subsequently and his date of death is unknown.
Conner's influence was limited by his personality, and his moral fervour was not matched by sophisticated analytical abilities. He had, however, grasped a central issue – that the tenants regarded themselves as possessing customary property rights in the land which it was both morally questionable and politically impossible to abolish. Though Conner was overshadowed in later memory by Lalor (largely because of the younger man's links with the separatist movement), both John Stuart Mill and Isaac Butt (qv) acknowledged his influence on their advocacy of Irish peasant proprietorship; Conner has been described as ‘the father of the three Fs’ of the Land League, and the land acts can be seen as the painfully delayed fulfilment of his advocacy of land reform through agitation coupled with parliamentary action. Although George O'Brien's tribute to him seems influenced by a desire to undercut the influence of the allegedly revolutionary Lalor, most modern scholars would agree with his verdict on Conner: ‘To have devoted the best part of one's manhood and the greater portion of one's fortune to fighting the cause of a class not one's own, and to have been the pioneer in the advocacy of measures long afterwards adopted by the greatest agrarian reformers of modern times, must surely be allowed to constitute some slight title to remembrance, if not gratitude.’
In 1852 R. R. Madden (qv) forwarded to Arthur O'Connor's lawyer in France, François-André Isambert, a petition on behalf of Conner, then in dire financial straits. Isambert, however, was dismissive of Conner's claim to be O'Connor's son.