The Queen sets foot on Irish soil today for the start of a historic state visit which will herald a new era in relations between Britain and the Republic.
Politicians on both side of the Irish Sea have described the four-day event as momentous.
When the Queen, joined by the Duke of Edinburgh, arrives in Dublin she will become the first British monarch to travel to the Republic in 100 years and the first since the nation gained independence from Britain.
An unprecedented security operation, costing an estimated 30 million euro (£26.2m), is in place to safeguard the royal couple, which includes land, air and sea patrols and a ring of steel around the centre of the Irish capital.
Some opposition to the royal visit has been voiced, which comes against a rise in dissident republican violence. But both the British and Irish governments say they hope the official trip will hasten a new and better relationship between the people of Ireland and Britain, built on equality and mutual respect.
Prime Minister David Cameron will join the Queen tomorrow for part of her trip, highlighting the importance of the visit, and Foreign Secretary William Hague will accompany the royals throughout their stay, as part of normal practice.
Irish president Mary McAleese, interviewed by state broadcaster RTE for a documentary to be screened tonight, said: "I think it is an extraordinary moment in Irish history. A phenomenal sign and signal of the success of the peace process and absolutely the right moment for us to welcome onto Irish soil, Her Majesty the Queen, the head of state of our immediate next-door neighbours, the people with whom we are forging a new future, a future very, very different from the past, on very different terms from the past and I think that visit will send the message that we are, both jurisdictions, determined to make the future a much, much better place."
Irish Taoiseach Enda Kenny has said the Queen will receive a "warm welcome" from the people of Ireland and that the public would have opportunities to meet her.
The royal tour will take in Dublin and the counties of Cork, Kildare and Tipperary.
In Dublin, the Queen will visit several politically and historically significant sites laden with symbolism such as Croke Park, the scene of a massacre by British troops, and the Garden of Remembrance, which honours those who fought for Irish freedom.
The Queen will also be guest of honour at events at Trinity College, the National War Memorial Gardens in Islandbridge, and the Guinness Storehouse.
Cork and Cashel are also on the agenda, along with a private visit to Coolmore, an international thoroughbred racehorse stud in Tipperary.
The Queen's grandfather George V was the last reigning monarch to visit the Republic in 1911 when it was still part of Britain.
The bitterness caused by the partition of the island a decade later and the use of the British Army in Northern Ireland strained relations between the UK and the Irish Republic for much of the 20th century.
But the success of the peace process has greatly eased tensions and a visit by the monarch is seen by many as cementing a closer relationship.
Sinn Fein president Gerry Adams stressed his party was still against the royal visit and would host celebrations of republicanism in each city the Queen visits. He described the visit as premature and insensitive.
Anti-war campaigners and left-wing republican group Eirigi, which has one council seat, are planning a series of protests.
The start of the visit falls on the anniversary of atrocities which claimed the greatest loss of life in a single day of the Troubles. Thirty-four men, women and children, including an unborn baby, were killed in no-warning explosions in Dublin and Monaghan on May 17, 1974.
The victims' families and survivors of a series of bombs have written an open letter to the Queen to mark her arrival in Ireland and will hold their annual wreath-laying ceremony a few hundred yards from where the Queen will commemorate Irish rebels in the Garden of Remembrance.
Justice For The Forgotten has appealed to the monarch to urge Prime Minister Cameron to open secret files which were withheld by the British Government during an inquiry.
Mr Cameron, in an interview with RTE, said the itinerary had been carefully selected to take account of a complex history.
"I hope she (the Queen) gets a very good reception. I think she will. The people in Ireland are kind and generous and compassionate," he said.
"I think 100 years on from the last time a British monarch visited Ireland I think there is a great sense of history and occasion.
"I think also the programme itself, which I think has been drawn up with immense sensitivity and care and thought by Her Majesty and by those working with her, I think that demonstrates an understanding of Irish history and all its complexity and I think that is absolutely right.
"But I think the real effect as I say will be a marker that just as we are solving some of the problems there have been between us in the past, just as we are helping each other through these difficult economic times, now is a great moment for people in Britain and people in Ireland to remember what it is we share."
The PM noted that 6 million people in the UK have an Irish grandparent, 100,000 British-born people live in the Republic and both nations reap the rewards of 3 million tourists travelling across the Irish Sea.
He added: "I believe Her Majesty's visit will be the start of something big."
Mr Kenny described the royal visit as a historic event which would symbolise the normalisation of relations between Ireland and Britain.
"This is a historic and symbolic visit dealing with the conclusion of the past and a message for the future," he said.
The Taoiseach said he did not know what would be in the Queen's speech to Dublin Castle - her only address this week - and refused to be drawn on speculation as to whether or not it would include an apology for Britain's past treatment of Ireland.
"I assume she will refer to the centuries of a different relationship between Ireland and Britain, but also to speak of the time to come where we know the way forward is by co-operation, understanding, doing business with each other as two modern countries, and as two peoples who want to get on with life, develop our economies and provide for the future of our families," he said.
The Taoiseach said there was no question of the royal visit being postponed on the back of security threats in London and outside Dublin.
While he defended the right to protest in a democracy, he said he did not want anyone to embarrass the nation during the tour.
Mr Kenny also insisted there would be extensive interaction between the monarch and Irish people despite a massive security operation banning any walkabouts and keeping the general public at some distance.Reuse content