`Have you ever noticed that Northerners are much quicker to take offence?" she asks. "There's a sensitivity there that is not quite as strong in the rest of Ireland, a sense that you're always going to be put down, a kind of prickliness. It makes for great humour but nevertheless, it's there, a very strange identity that has real reasons behind it."
The brutality wasn't always one-way of course and Elliott squares up to it - be it the murderous, freebooting, local captains of 1641 or the Provos. For her, the defining moment in what for Northern Ireland was the defining century, was the 1641 rebellion. "This was when the idea was created that Popery was out to destroy Protestantism . . . And there's no doubt that the Ulster Catholics did massacre the Protestants, even though it got out of control and it wasn't as big a bloodbath as it has been portrayed." Contemporary propaganda claimed 150,000 Ulster Protestants died when there were no more than 30,000 in the entire province. Of those, however, a staggering 12,000 may have perished, leading to terrible retaliation in the short term, then to the Penal Laws, and most damagingly of all, to "the great shadow behind the insecurity which is the Protestant mentality".
That mentality was further exacerbated by the distance created between the Protestant gentry and the socially inferior Catholics. The obliteration of the Ulster Catholic gentry and the fact that Ulster never had a significant Old English class - an elite accustomed to the practice of power and politics - meant that the Protestant gentry there never had to deal with equals. The resulting gulf bred further Protestant fears of subversion - fears which Elliott believes were "unrealistic".
For, as she points out repeatedly, the Ulster Catholics are not natural rebels. In the middle of the last century, she writes, Catholics were as conservative and predisposed to authority as they had ever been. 1961 failed largely through the lack of Catholic support. And all the way through, says Elliott, the Northern Church - always with its finger firmly on the people's pulse - had been solid in its condemnation of IRA violence. "In all our celebrations of rebels in Irish history, we are celebrating a very tiny section, very tiny. It came as a great revelation to me that there were points in Irish history where, had the Catholic church and the emerging Catholic nation been taken on board and brought into the system, we would have had quite a different state."
One such might-have-been, in her view, was in the 1790s, when a secular Catholic leadership could have been peacefully incorporated into the state. Another, she believes, was Sunningdale. "Back in 1974, the Provos hardly existed; we wouldn't have needed to bring them on board. I still feel that what was on offer then was what the Catholic community was looking for, if it had just been given time to work, if they had been made to feel that they had some control, some sense of belonging, of ownership."
Did any of the issues confronting her in her research cause her, personally, to flinch? "Yes," she answers immediately. "Catholic education." From personal experience, she characterises it as "psychological crippling . . . where the individual was crushed out". "I have no doubt that it came against me in university. Also it took me a long time to get a career established; it didn't take very much to knock whatever self-confidence I ever had. Northern Catholics on the whole do not have much self-confidence."
Even now, although the ghetto church may be gone - moving on to wield considerable influence both within the state and in a slew of opinion- and policy-forming bodies - it still seems, in Elliott's eyes, profoundly authoritarian on religious issues, and above all on education.
But in the North, to criticise your own is still unthinkable, she says. "It was part of the community's protective mechanism, because they didn't see the institution that was keeping them down as the Catholic church; they saw it as the Protestant state. And that meant that the Catholic church had an awful lot of power in the North. But at the same time, there were times when I saw that the Catholic community needed the church. The church spent over a century developing totally alternative institutions to the State which most of the Catholics of the North were perfectly happy with; an alternative state. And while the Catholics didn't feel very involved in the State, it was important for them to have that."
In any event, no real questioning will start, she says, until the Northern Catholics feel totally accepted and equal. For Northerners, such questioning involves a great deal more than simply criticising the church's power complex. The intertwining of Catholic religious and political culture goes back 300 years, to when power became Protestant, making the have-nots the Catholics, and Catholicism in nationalist folklore become a pre-requisite for Irishness. "Today's nationalists in Northern Ireland", writes Elliott, "do not define their identity in anything other than cultural and political terms and are irritated by outsiders who more accurately portray it as religious. This is because that religion was so successfully subsumed into political culture over 300 years ago."
The Troubles shattered some of those old certainties, propelling nationalists into a painful process of self-examination, during the hunger strikes for example, when nationalist politicians and Catholic bishops felt themselves being pulled into being apparent spokesmen for a tradition of violence which they abhorred; or ordinary Catholics expressing a justified distrust of the police, say, who then found themselves open to accusations of being apologists for IRA actions.
"In many ways, it is only the extreme republicans who have retained the old identity," writes Elliott, "and they blame everyone but themselves for the widespread questioning of the myths which once gave meaning to real sufferings". But, lest we forget, their readings of the past were not mere self-delusion; they were based on the constant drip-feed of the Catholic press and other Catholic writings for much of the 20th century.
No-one can afford to be smug. "Everybody is sectarian in Northern Ireland, to some extent or another," says Elliott.
"The anti-Catholicism which underpins the Ulster Protestant identity is still there and I'm not even sure that a lot of Protestants realise it's there. It's as much a part of their identity as anti-Englishness is a part of nationalist identity. Protestants have always seen Catholicism as a threat to their entire culture; that's been there since the outset. "Catholics are no less sectarian though their sectarianism takes a different form; it's not the religion itself but its representation in the State that they dislike so much. But in many ways, they're both equally nasty. It's just because religion has been such a strong part of our Catholic identity for so long, that Catholics think that only Protestants are bigoted."
The decades-old debate in the Republic, questioning the anti-English underpinnings of our nationalist past, was "a necessary prerequisite to the emergence of the now confident Irish state as a player in world politics," she says. But then again, "it was easier for the Republic to exorcise the ghost of the long-absent British. In the North, the people held responsible for the land confiscations and persecutions are one's neighbours." "But it's high time to move on, . . . high time for Ulster Catholics to re-assert their regional identity and challenge the view that `Ulster' necessarily means Protestant . . . High time that we `poor powerless people' of Ulster stopped blaming everyone else for what has happened and took control of our future by accepting responsibility for our past. In doing so we should recognise that those political leaders, which so often in the past we have blamed for our problems, have already moved a long way from the attitudes described in this book."
And so, by the way, has Marianne Elliott, the Northern Catholic who finally overcame that old "psychological crippling" to become Andrew Geddes and John Rankin Professor of Modern History at the University of Liverpool and director of the Institute of Irish Studies. In a few weeks' time, in the company of her English-born husband of 25 years, their young son and her mother, she will step up to receive an OBE in recognition of her contribution to Irish Studies and to the Peace Process. And within hours of that, she will launch her book in Belfast's City Hall.
"It's kind of symbolic," she grins delightedly. "It's taken an awful long time for Catholics to get into City Hall."
The Catholics of Ulster: A History by Marianne Elliott will be published shortly by Allen Lane/Penguin Press (£25 in UK).