It depends how far back you want to go!
Yes to the Normans (and Irish King of Leinster Dermot McMurrough) for the subjugation of Irish kings.
Yes again to James I/ Elizabeth/ Cromwell for the plantations.
In more modern times the Home Rule Crisis is often forgotten. This was a movement by Irish nationalist politicians in the House of Commons to give Ireland limited self government (similar to devolution). It was supported by the Liberal leadership under Gladstone and later Asquith. The stories were opposed for a number of reasons including family links and business interests. This grew exponentially during the Third Home Rule Crisis from 1911 onwards when the Tory leader Bonar Law made it clear that the Torres would support Ulster Unionist opposition to Home Rule no matter how far they took it. (Partly as a unifying issue for the divided Conservative party- sound familiar
) This galvanised Unionist opposition under Carson and Craig and soon the UVF was founded, followed by their nationalist counterparts the Irish Volunteers, making the prospect of Civil War in Ireland a possibility. Along with the First World War And a weak nationalist leader in John Redmond this led to partition being enshrined before the Irish War of Independence had truly been acknowledged as a War (rather than the work of criminal murder gangs as Lloyd George put it)
The new state of Northern Ireland was designed to have a Unionist majority and the British government were happy to let them get on with running the country. However it was discriminatory from the start. This came to a head in the 1960s when the minority Catholic population, motivated by peaceful civil rights movements in the US and now having had the benefit of free education began to protest.
As in the Home Rule crisis these protests were met with opposition from the Unionist community who organised counter marches to clash with civil rights protests which often led to attacks on Catholic area afterwards, sometimes with the participation of off duty RUC men. Wound up by Unionist leaders such as Ian Paisley and depicted as a Catholic rights organisation many Unionists were strongly opposed the NICRA, a non sectarian organisation. (Many unionists such as Gusty Spence- UVF leader- acknowledged later that they were misled by their leaders and should have been involved in NICRA not in opposition to it.
The growing sectarian conflict (which was really about nationalism, not religion) was of concern and embarrassment to Britain who sent in the army to protect Catholic areas from attack and as PPs have mentioned were welcomed. That all changed when they were put under the control of the Unionist government who used them in the same way as the RUC. A clear turning point was the Falls Curfew in 1970 followed of course by Ballymurphy, Bloody Sunday and Internment. All these issues led to the growth of the IRA who had little to no support prior to 1969, who split into the provisionals and stickies and the provisionals in particular became more active. The actions of the British Army made easy propaganda for the PIRA to show that they were the real protectors of Catholic communities. All of these also led to poverty both of expectation and actual poverty (due to high unemployment) and the growth of the paramilitaries (on both sides) particularly in working class communities in Belfast and Derry b
So in summary- British leadership, a divided Tory party supporting any actions by Ulster Unionists, weak nationalist political leadership, manipulation and propaganda by Unionist leadership coupled with British indifference and the actions of paramilitaries on both sides along with the British Army with a side dish of biased media reporting and poverty. There are some striking parallels to Brexit which is concerning but history ever repeats itself