The heck? Goddamn americans, never seeming to realise that the greatest oppressors of ireland have been the irish (some of whom had english support, in terms of funds and armies)
Okay lets look at irish history
116715th cen Norman Ireland
-Invited by an exiled irish king
-Feudal system, Lordship of Ireland, Irish-Norman Lords
-Not a dictatorship in the modern sense, not any worse than the rest of europe or ireland before the normans came.
Lordship of ireland passes to the Fitzgerald Earls of Kildare (15th cen)
-Enforces rule with military might
-Close to dictatorship, but these guys are as irish as they come.
Tudor Reconquest of ireland (1536-16th cen)
-Various solutions tried, including federal and local military forces, and the Colonist plantations
-Again the system was mainly feudal and the people did have some rights
-Eventual resulted in rebellion, war and spanish interference to end in a centralised government.
-Catholics discrimnated against but protestants irish encouraged.
Rebellion of 1641-53
-catholic gentry revolted, set up confederate ireland, a rather nasty government that killed thousands of protestants, somewhat dictatorial.
-1649-53 Cromwell brutally reconquers it, again somewhat dictatorial
Williamate war (1689-91)
-Protestant irish elite crushes catholic ireland with british backing
-Ireland mainly run with an irish parliament (dominated by absentee landlords) from now till the act of union (oppressive, but not dictatorial).
-Due to english predominace in parliament, ireland is neglected and abused
Act of Union 1801-1910
-Merger of the irish and British parliaments, later catholic emacipation, not a dictatorship again.
-Irish famines, not due to the evil english, but more due to (Katrina style) incompetence and apathy.
-Irish parliamentarians advocate home rule, industrial protestant ireland against this, catholic agarian ireland for it. Massive screw ups lead to.
1916-21 period of violence and upheavel, most of ireland gains independence except for ulster where the majority of the population wanted to stay in the union.
So no, you can't really say ireland has been under a dictatorship since Cromwells time. Abused by london and their own protestant elite yes, but not a dictatorship as your crude terms would apply it - the rule of law has been pretty well maintained. Ireland was under a dictatorship in much the same way the postbellum american south was under a dictatorship.