The professor of Irish history cannot hide his relief at being able to offer a simple answer. It is a scarce thing in Dublin this week.

The parallels between Australia's bloody debut on the world stage in 1915 and the doomed six-day rebellion against British rule that shattered Dublin a year later are certainly compelling.

But Australia never put on a commemorative show like the one Ireland is staging this weekend to remember April 1916.

Dublin looks like an Easter Rising theme park; banners hang from lamp posts everywhere, special tour buses prowl the streets, houses are decked out with buntings and flags, there are billboards and murals, radio, TV and newspapers talk of little else, museums and galleries are given over to The Rising, shops and street stalls sport ranges of 1916 memorabilia and, of course, the pubs are in on the action.

On Sunday and Monday tens of thousands, maybe more, will throng central Dublin for the biggest deal in Irish public life since anyone can remember. It is an overwhelmingly state-sponsored and scripted affair.

"They got this thing screwed down pretty tight," an American visitor observes.

But you cannot control talk, not in Ireland, and the legacy of the short-lived insurgency a century ago by about 1500 fringe dwellers of Ireland's nationalist movement is still fiercely debated in Ireland, much more than Australians discuss or clash over the finer points of the Anzac legend.

When the Irish rebels struck, Australia was still reeling from its losses at Gallipoli and much worse was to come on the Western Front.

But a small number of Australians spent the first Anzac Day, April 25, 1916, fighting in the streets of Dublin after being hastily drafted into the British Army's effort to crush the insurgency.

Dublin was a popular destination for Diggers on leave, with Ireland mercifully free from the harassment commonplace on the British mainland from overzealous military police.

But when the insurgents sprung their plans on the unsuspecting city on April 24, seizing a number of key buildings around town, any man in a British or dominion army uniform came under fire and was sent scuttling for cover.

A small group of Anzac and South African soldiers took refuge in Trinity College, armed themselves with the rifles of the uni's student militia and took up commanding firing positions on the college roof.

When the Anzacs, among them Queenslander Private Michael McHugh whose parents were from County Galway, were given orders to fire at will, the first man they shot down was young Gerald Keogh.

The idealistic member of the main nationalist force group, the Irish Volunteers, was riding his bicycle between two nationalist positions when he found himself in the sights of the Gallipoli veterans, whose accurate fire appears to have killed the young rebel instantly.

A century on, Keogh's great-nephew Raymond Keogh surveys the scene of the shooting and talks about his own personal struggle to make sense of the pre-dawn killing.

"When those Anzacs went into Trinity they hadn't had a clue what was going on, but they would have been so attuned to being part of the British military, that they would not have thought twice about going onto the roof of Trinity and defending it against a possible onslaught," Keogh says.

"I certainly think they weren't guilty of any misdemeanour or malice and this is what makes Gerald Keogh's death so meaningless.

"It points to the meaninglessness of war and the tragedy of war and if there's some way of passing beyond this terrible dilemma that both of them were involved in."

Raymond Keogh is not alone in hunting for meaning in the Easter 1916 story; just metres away from the spot where Gerald Keogh died, Trinity historian Eunan O'Halpin has just wrapped up yet another media interview.

The "go-to" professor has spent much of this week trying to explain to the world what the fuss over Easter 1916 is all about, and the message is that all the state-sponsored pageantry and pizazz contains a steely streak of realpolitik, more to do with Ireland's complex present than its tangled past.

The Irish state, now without a government after an inconclusive election in February, has been in a tug of war with the country's persistent republican dissident movement, Sinn Fein, over the legacy of The Rising.

Sinn Fein, founded in 1905, was the political driving force behind The Rising but for many in Ireland, the modern version of the party led by Gerry Adams is tainted by its close links with the Provisional IRA terrorist group.

The Irish state brings the overwhelming force of its money and institutions to the struggle for control of The Rising, but as usual it can't entirely quell the insurgency.

For O'Halpin, the Irish state had no choice but to co-opt The Rising's anniversary.

"Because this is the most potentially political centenary, I think the state quite rightly has been very active in promoting the centenary because if they don't, basically the republicans will come along and do it for them," O'Halpin told Fairfax Media.

O'Halpin believes a sovereign state has a tricky time taking ownership of an event that can be seen as a murderous attack on an unsuspecting democracy by a fringe group bent on using violence to achieve their minority political goals.

The task is made trickier still by the reality that The Rising put the gun front and square in Irish politics and that, even after 100 years, it has not entirely gone away.

"The point about 1916 is ... for the Provisional IRA, until 1998, it was a core principle of theirs that they were the legitimate successors of 1916, not only in terms of physical force but that they were the government and parliament of Ireland," O'Halpin says.

"This absurdist theology ignores the functioning of Irish democracy since independence."

While they exchanged fire with the Irish Volunteers, McHugh and the other Australians in action around Dublin had no idea the battle was lighting a fire back home that would burn for decades.

Sectarian tension in Australian society had been put largely put aside for the sake of the war effort, but The Rising put an end to the harmony, University of NSW historian Jeff Kildea says.

"It marked a watershed," Kildea says.

"Chronic sectarianism in Australia had become quite acute in the pre-war years, had been largely put aside as most of the nation, Catholics and Protestant, put aside their difference and united behind the war effort.

"That truce lasts about 20 months, until the Easter Rising."

The author of Anzacs and Ireland says the subsequent bitter national disputes about conscription and other social issues that divided Australia had their roots in the backlash against The Rising.

Crowds will gather for several ceremonies around Australia this weekend to mark the centenary.

Next week, the Keogh extended family will hold a small ceremony in Dublin honouring their fallen young Irish Volunteer.

In Ireland there will be a big party and nothing will be resolved. But as they say in Ireland, sure isn't it something to talk about.

The writer travelled to Ireland as a guest of the Irish Department of Foreign Affairs and Trade.