Although the Queen's flight from London to Dublin took less than an hour yesterday, it was a full century in the making; Britain and Ireland only now deciding that the timing was finally right. The plane touched down at noon, its royal standard fluttering in the breeze, signalling the first visit to Ireland by a reigning British monarch since George V in 1911.
The Queen's four-day mission, as agreed after meticulous discussions, is to sweep away the cobwebs of history which have for so long bedevilled relations between the two countries.
It is to signify that the Irish peace process is all but complete: the two governments hopeful that this initiative will herald a new beginning in Anglo-Irish relations.
It was once common in Ireland to hear Britain referred to as "the old enemy". This is heard less often nowadays but the hope is that, apart from a handful of hardliners stuck in the past, the concept will lose all meaning.
Yesterday's events included a moment of genuine history when the Queen honoured Ireland's patriot dead by laying a wreath at the city's Garden of Remembrance. Amid solemn military ceremony, complete with a gleaming sabre pointed dramatically towards the sky, the British and Irish national anthems were played.
In a landmark moment, the monarch commemorated "all those who gave their lives in the cause of Irish freedom" – that is, those who took up arms against her forebears down through the centuries. The garden has a cruciform water feature, which includes depictions of broken swords and shields that signify the end of conflict.
A long-standing Irish grievance is that some of those who took part in rebellions against the British were executed by the authorities, particularly after the much-venerated risings of 1798 and 1916. The Queen's gesture can be interpreted as an implicit recognition that they had a legitimate cause.
Today an element of balance will be introduced when she commemorates the thousands of Irishmen who died in British uniform in many conflicts. But there will also be a moment of even more powerful symbolism when she goes to the sports stadium where police and troops shot dead 14 civilians in 1920.
The public reaction to her visit was difficult to judge yesterday, since thousands of police were drafted in as part of the most stringent security operation Ireland has ever seen.
Much of central Dublin was practically deserted as large swathes of the city were sealed off. The Queen, who travelled in a large-scale security convoy, would have seen little of the general public.
At several spots, well away from the royal party, scuffles broke out between republican protesters and police, who used pepper spray during at least one confrontation. In another incident stones and fireworks were thrown at police officers. Dissident republican terrorists were also active, leaving a bomb on a bus outside Dublin. It was discovered and dealt with by army experts. Its target is unknown.
Sinn Fein registered a symbolic protest by releasing black balloons during the ceremony at the Garden of Remembrance. A spokesman, who said that the visit was premature and offensive, declared that "almost 400 people have been killed in Ireland by the forces of which she is commander-in-chief".
But the general impression was that most of the population either approves of the visit or has no particularly strong feelings about it. Official Ireland, however, strongly advocated it, viewing it as an opportunity to set the seal on the peace process.
The desire to convey a sense of mutual respect was evident from the moment the Queen walked down the steps from her plane wearing a coat and hat both of which were in bright Irish green.
She has visited more than 120 countries during her reign, but this was the first time she had ever made the short hop across the Irish Sea to Britain's closest neighbour.
Accompanied by a retinue that included the Foreign Secretary, William Hague, she was presented to a series of dignitaries at a military airbase named after Roger Casement, a nationalist hero who was executed for treason in 1916.
Hundreds of security forces surrounded the airport, which is thought to have been guarded by radar equipment and surface-to-air missiles.
She then had lunch at Aras an Uachtarain, once the residence of British viceroys who ruled Ireland, and now the official residence of the President of Ireland, Mary McAleese.
The Irish flag and the Union Jack flew side by side while the national anthems of both countries were played and a 21-gun salute was fired.
Tonight the Queen is to deliver a speech in which she can be expected to refer, highly diplomatically, to some of the difficulties of the past. The Prime Minister, David Cameron, who will also be in Dublin, may make more political comments.
He is already something of a nationalist hero for his forthright apology for the actions of troops on Bloody Sunday in Londonderry in 1972, and is unlikely to let pass an opportunity to address past events and lay them to rest.
The Taoiseach of Ireland, Enda Kenny, said of the visit: "In effect it is history in the making, a new chapter in Irish-British relations that will be both significant and historic."
When King George V crossed the Irish Sea
The Queen's grandfather, King George V, brought with him a flotilla of battleships and destroyers during the last visit to Ireland by a reigning British monarch.
That was in 1911, when Britain used its seapower to sustain the British Empire, which then included Ireland. Part of the purpose of the King's visit was to impress the world with its power, and many locals were indeed impressed, flocking to the shore to marvel at the Navy's Dreadnoughts.
In 1911 "God Save the King" was played for him at St Patrick's College at Maynooth, where Catholic priests were trained, by the Artane Boys' Band.
The warm reception and cheering crowds which greeted George came as little surprise, for royalty had long been popular with many, probably a majority, in Ireland.
The irony was that, just over a decade later, following a tumultuous period of rebellion, British troops were on their way out of Ireland and southern Ireland was on its way to independence.
George fondly recalled previous happy times in Ireland as a naval midshipman, one of a series of royal links with Ireland both before and after British withdrawal.
Queen Victoria, for example, visited four times, though in all spent just five weeks there, preferring to spend time in Scotland.
David McKittrickReuse content