Let me explain it to you just once but if you show any indication that you can't rise above the Catholic Protestant thing.... I'm outa here.

It was common practice for the British (English really) to invade foreign lands using various strategies, form Governments and claim them as part of the British Empire. In order to maintain control over such places, far from home and with only wooden boats to get you there, it was imperative that a large number and not usually the majority were onside with you. In order to make this a reality, this would mean that those whom you had chosen must be given some kind of unfair advantage over the majority. Land, wealth & the power to police and otherwise control the population.
Once this has been established the Invaders are now free to sit back and strip the country of whatever riches it can provide.
When the majority revolt and they always do, whom do you suppose is their target? Not the well armed, occupying forces but their own countrymen who have profited so much by their allegiance with the foe.
Britain, in the meantime, sits back and says to the world "Look! It's not our fault. Those Sikhs & Muslims just can't get along."
Now Ireland is fairly unique and most unfortunate in that it is fairly close to England. Thus the tactics were changed a little. Ireland was a Catholic country but more than that IT WAS IRISH! Being so close to home it was no problem recruiting as many armed forces as it took to maintain control. Added to that it was even more practical to encourage those recruits to stay by offering them land, wealth and power over the Irish. The unfair advantage.
And there you have it. Yes, the Irish are Catholic and Yes, the invaders were Protestant but more importantly, they were mostly Scots & English.
And what does the British Government do? It sits back and says to the world "Look it's not our fault. Catholic and Protestant just can't get along"
Now Keith: I'll give you one small example of how the unfair advantage worked and this one was the trigger for the troubles that go on to this very day.
In 1969 there were several marches, led by an extremely charismatic individual by the name of Bernadette Devlin. Her arch rival was none other than the Reverend Ian Paisley.
The slogan was "One Man, One Vote".
You see Keith, at that time, the vote was assigned to the household, not the individual. What this meant was that if you rented your house then the vote belonged to the landlord. And who owned the land. The privileged few. The sons and grandsons and great grandsons of the invaders. A simple law (And there are/were many more) that kept them at each others throats for centuries because once they owned the land and the people on it, there was no way for the unfortunate Irish to get it back.
Now today there may be a slim "Protestant" majority in Northern Ireland and you ask ... "If there was going to be a partition, surely it was right to only separate those counties, and parts thereof, where there was an overwhelming majority who wanted to remain British?" and I would have to say to you that those people of Northern Ireland whose forefathers invaded that country and who refuse to be loyal to what is the land of their birth, owe their very existence to THE UNFAIR ADVANTAGE!