Convinced that the measure was essential to maintain order in Catholic-majority Ireland, the Duke of Wellington helped overcome the opposition of the King, George IV, and of the House of Lords, by threatening to step aside as Prime Minister and retire his Tory government in favour of a new, likely-reform-minded Whig, ministry.

Their investment enabled O'Connell to mount "monster" rallies (crowds of over 100,000) that stayed the hands of authorities, and emboldened larger enfranchised tenants to vote for pro-emancipation candidates in defiance of their landlords.

To overcome the vehement opposition of both the King and of the House of Lords, Wellington threatened to resign, potentially opening the way for a new Whig majority with designs not only for Catholic emancipation but also for parliamentary reform.

For the Oath of Supremacy, the act substituted a pledge to bear "true allegiance" to the King, to recognise the Hanoverian succession, to reject any claim to " temporal or civil jurisdiction" within the United Kingdom by "the Pope of Rome" or "any other foreign prince ... or potentate", and to "abjure any intention to subvert the present [Anglican] church establishment".

[19] Receiving its royal assent on the same day as the relief bill, the act disenfranchised Ireland's Forty Shilling Freeholders, by raising the property threshold for the county vote to the British ten pound standard.

In Clark's interpretation, the system remained virtually intact until it suddenly collapsed in 1828, because Catholic emancipation undermined its central symbolic prop, the Anglican supremacy.

Clark argues that the consequences were enormous: "The shattering of a whole social order ... What was lost at that point ... was not merely a constitutional arrangement, but the intellectual ascendancy of a worldview, the cultural hegemony of the old elite.

Paradoxically, Wellington's success in forcing through emancipation led many Ultra-Tories to demand reform of Parliament after seeing that the votes of the rotten boroughs had given the government its majority.

Thus, it was an ultra-Tory, the Marquess of Blandford, who in February 1830 introduced the first major reform bill, calling for the transfer of rotten borough seats to the counties and large towns, the disfranchisement of non-resident voters, the preventing of Crown office-holders from sitting in Parliament, the payment of a salary to MPs, and the general franchise for men who owned property.

But in breaking the link between Catholic inclusion and democratic reform, the terms under which he was able to secure the final measure of relief may have weakened the case for a restored Irish parliament.

[30] Seeking, perhaps, to rationalise the sacrifice of his freeholders, O'Connell wrote privately in March 1829 that the new ten-pound franchise might actually "give more power to Catholics by concentrating it in more reliable and less democratically dangerous hands".

In a pattern that had been intensifying from the 1820s as landlords cleared land to meet the growing livestock demand from England,[33] tenants had been banding together to oppose evictions, and to attack tithe and process servers.

In February 2025, the UK Government introduced a bill in the House of Commons to repeal a clause from Section 12 of the Act, to allow Roman Catholics to hold the office of His Majesty’s High Commissioner to the General Assembly of the Church of Scotland.