Irish president Michael D Higgins' four-day state visit to the UK, the first for an Irish head of state, is another milestone in Anglo-Irish relations.
Over the years and centuries, it is a relationship that has been marked by insurrection, war and strained diplomacy despite geographical proximity and many cultural and familial ties.
Early days of English rule
The Norman invasion of Ireland in the late 12th Century marked the beginning of 700 years of shared history between neighbouring islands separated, at their furthest, by about 150 miles.
The English Crown did not assert full control of Ireland until 1541, when the Irish Parliament bestowed the title of King of Ireland on Henry VIII after an uprising by the Earl of Kildare threatened regal hegemony.
The arrival of thousands of Protestant settlers from England and Scotland displaced many of the existing Catholic landholders and sowed the seeds for centuries of on-off sectarian and military conflict.
Wars in the middle and end of the 17th Century cemented the Protestant ascendancy, with William of Orange's victory over James II in the Battle of Boyne in 1690 both celebrated and mourned to this day.
The Irish Parliament was abolished in 1801, with Ireland becoming a part of the new United Kingdom of Great Britain and Ireland under the Act of Union.
The Great Potato Famine of the 1840s, in which a million people are estimated to have died and led a further two million to emigrate, is regarded by many as a turning point in relations between the countries.
The birth of a nation
The second half of the 19th Century was marked by the rise of competing nationalist movements and battles over home rule which decided the fate of British prime ministers.
Those seeking a constitutional route to self-government were rewarded with the restoration of home rule in 1914 - although this was soon suspended at the outbreak of World War I.
More than 200,000 Irish men fought for their King and country in the conflict, almost a quarter never to return.
It was against this turbulent backdrop that those who believed that armed struggle was the only way to achieve their ultimate goal of independence for Ireland asserted themselves.
The Easter Rising of 24 April 1916, which was brutally dealt with by the authorities after hopes of German assistance did not materialise, remains to this day the most symbolic manifestation of this fight.
The 1919-21 Anglo-Irish War which followed saw numerous atrocities on both sides, by a nascent Irish Republican Army (IRA), whose leaders included Michael Collins, and a British government whose authority was waning.
The agreement which eventually led to the 1922 partition of Ireland and the creation of the Irish Free State, remained a source of division for 70 years.
Michael Collins only outlived the signing of the Anglo-Irish Treaty by nine months, gunned down during the civil war that ensued, while David Lloyd George quit as prime minister a few month later.
The "No Blacks, No Irish, No Dogs" signs displayed in boarding houses in British cities in the 1950s and 1960s seem part of a distant era now but were a virulent symbol of the distrust between the two countries.
While sectarian tensions were not new in Northern Ireland and IRA attacks on parts of Britain dated back to 1939, the 30-year conflict known as the troubles was of a different magnitude altogether.
Events such as Bloody Sunday, the hunger strikes, the bombing of the Conservative Party conference at Brighton and the Omagh bombing are seared on the consciousness of a generation, whatever their political and sectarian loyalties.
The root causes of the conflict will continue to be pored over, but the true toll in terms of human suffering may never be known.
It is estimated that more than 3,600 people were killed during the violence between 1969 and 1998.
The vast majority of deaths were in Northern Ireland, but more than 100 people are estimated to have been killed in other parts of the UK and also in the Irish Republic.
After decades of strife, the 1985 Anglo-Irish Agreement was a ground-breaking moment, as much for its symbolism as for its actual impact.
Signed by British Prime Minister Margaret Thatcher and her Irish counterpart Garret FitzGerald, it paved the way for regular conferences between British and Irish ministers on matters affecting Northern Ireland.
This gave Dublin a role in Northern Ireland for the first time in more than 60 years.
The fruits of this closer co-operation, although resisted by some at time, were felt later as international support for the peace process in Northern Ireland gathered pace after the 1994 IRA ceasefire.
The 1998 Good Friday Agreement, which reaffirmed Northern Ireland's constitutional status in the UK while also repealing the law by which Ireland was partitioned, was approved by 94% of Irish voters in a referendum.
The Crown and Ireland
Before her successful state visit in 2011, Ireland was one of the few countries that the Queen had never visited in an official capacity.
This was evidence of the legacy of historical recrimination and mutual suspicion which until recently existed between the two countries.
Despite becoming a self-governing dominion in 1922, the Irish Free State remained a member of the British Empire, with the British sovereign remaining as head of state.
Ireland became a fully independent state in 1937 but did not withdraw from the Commonwealth until 12 years later. The prospect of rejoining has never been seriously pursued.
However, the Queen's 2011 visit - in which she paid her respects to republican dead and gave a speech on Anglo-Irish history - drew near universal praise and the prospect of members of the Royal Family attending events for the centenary of the Easter Rising is being entertained.
Sporting and cultural bonds
The long sporting rivalry between Ireland and the UK's "home nations" has often transcended politics but it has, at times, also encapsulated historic shifts in attitudes.
When God Save The Queen was played at Croke Park - the scene of an infamous police massacre of civilians during the Anglo-Irish War - before a rugby match in 2007, the absence of any booing was seen as a pivotal moment in the long process of reconciliation.
Whether it is the shared passion among fans for the Six Nations or the Cheltenham Festival, Anglo-Irish battles are now fought out on very different turf indeed.
Patterns of emigration have ebbed and flowed over the years but more than 400,000 Irish citizens call London home and there are large, vibrant Irish communities in most of England and Scotland's largest cities.
The great Irish writers of the 20th Century, such as Samuel Beckett and James Joyce, preferred Paris to London, but the lure of London as a literary destination has grown in recent decades.
Michael Gambon, Pierce Brosnan, Graham Norton and Terry Wogan, are among the many members of the Irish Diaspora who have become pillars of the theatrical and showbusiness establishment.
Ireland leads the UK by seven victories to five in the Eurovision song contest.
Financially, the UK and the Irish Republic are now intertwined as never before.
The Irish Republic is the UK's fifth largest trading partner, while nearly one in five exports leaving Irish shores is destined for the UK. In total, bilateral trade between the two is close to £30bn.
There are 50 Irish businesses listed on the London Stock Exchange, including packaging giant Smurfit Kappa, food ingredients maker Kerry Group and bookmakers Paddy Power, while one of Ireland's most famous exports, Guinness, is owned by British drinks firm Diageo.
The way in which the two economies are emerging from the recession caused by the 2008 banking crash at a similar rate points to the similarities and mutual interests between them.
It was telling, at the height of Irish economic woes in 2010, that the UK Parliament approved a multi-billion loan to Dublin with few if any dissenting voices at a time when "EU bailout" was something of a dirty word.
As Britain stands on the threshold of exiting the European Union, a paean to Brussels has been made public, in which the author, former British ambassador to Ireland Sir Ivor Roberts, attributes the warming of Anglo-Irish relations during his tenure in Dublin to the influence of the EU.
In a valedictory dispatch to the Foreign and Commonwealth Office in London, which has been released under the UK’s freedom of information legislation, Roberts extols the influence of Brussels.
The EU is praised both in terms of the helpful effect it had on specific and often thorny details of Anglo-Irish relations, as well as in the way in which membership of the body brought the two countries together, working as allies within the bloc.
About 1,600 words long, some 400 of which have been redacted, Roberts’s dispatch, written in April 2003 as he prepared to leave Dublin after four years as ambassador, begins with the staccato observation: “Ireland a much-changed country.”
He continues: “What fundamentally changed the way [Britain and Ireland] looked at each other was our common membership of the European Community, whose fresh winds dispersed the dank claustrophobia which had so soured the relationship.
“EU membership has served to highlight the many areas where the UK and Irish interests are similar; and we have developed the habit of working together. As a result, the inelegant word normalisation has become a strategic objective of the relationship.
“But what does normalisation mean for the practitioner? I have seen at first hand the development of the extremely warm and cordial personal chemistry between the prime minister [Tony Blair] and the taoiseach [Bertie Ahern]. It is this which sets the tone for the bilateral relationship more broadly.”
He sets out examples, most of them relating to high-profile events with a British royal or military flavour.
These include: the joint unveiling in 1998 by Irish president Mary McAleese and Queen Elizabeth of a memorial to all from Ireland who died in the first World War; the exchange of national-day greetings between both heads of state (“now possible,” Roberts notes, “following the removal from the Irish Constitution of the territorial claim to Northern Ireland”); the first visit to the Republic of the Irish Guards; the address to the Oireachtas by Tony Blair; the 2002 visit by Prince Charles to the Glencree Centre for Peace and Reconciliation; and the frequency with which Royal Navy warships docked on the river Liffey while their captains dispensed entertainment, an event “now so routine as to be barely worthy of comment”.
“I found it remarkable,” he writes, “that the Irish Tricolour flew at half-mast over government buildings, including the GPO in O’Connell Street, as President McAleese attended the funeral of the Queen Mother.
“And, bathetically, when I snatched a rare round of golf at the K Club recently, for the first time, the union flag was flown beside the Tricolour.”
Towards the end of the valedictory statement, he returns to the benevolent effects of British and Irish membership of the EU; “subterranean trends”, as he calls them.
“One is closer co-operation on European issues,” he writes.
“Not just in policy areas, such as social security, tax, justice and home affairs and the Lisbon agenda of economic reform, but also in the Convention on the Future of Europe, which is preparing the ground for the 2004 Intergovernmental Conference.
“British and Irish co-operation will be imprinted on what could, I believe, turn out to be a treaty of Dublin. This is a far cry from the days when Irish officials were instructed to speak French at EU meetings.”
The conference eventually produced the EU constitution, but it was signed in Rome, not Dublin, in October 2004 and rejected the following year by voters in France and the Netherlands, leading instead to the Lisbon Treaty in 2007.
Roberts notes how different a place Ireland was for a British diplomat in the decades preceding his tenure.
“The Ireland I visited in the 1970s was not a comfortable place for a British diplomat. Venturing into rural pubs, we were as likely to encounter outright hostility as the fabled Irish welcome,” he writes.
He detects also a sense of shame among many Irish people at the 1976 IRA murder of one of his predecessors, Sir Christopher Ewart-Biggs, together with an assistant, 26-year-old Judith Cooke.
“It is one of the endearing traits of the Irish that there are many people who still tell me how shocked and ashamed they were by the events of that day over a quarter of a century ago,” he writes.
On the threat of the IRA, he notes that in the early 1990s “our guesstimate of the scale of the Provisionals’ threat was around 900”, but the organisation was coming to realise then that it could not achieve its aims militarily.
“This was an enormous change in position by the republicans and it is proper and right to acknowledge the extent of it.”
That said, the former ambassador reminds his readers that while Sinn Féin signed up to the Belfast Agreement, the party did not see it as an end in itself but rather as a “transitional phase”.
The redacted parts of the valedictory appear in the main to relate to observations on the changed stance of Sinn Féin and the IRA (leading in the South, he suggests, to it being “respectable again to be a republican nationalist”), and to some observations about the Irish economy.
“Now the Celtic Tiger has run out of puff, and while the Irish economy defied the laws of gravity for nearly a decade, the downturn in the world economy and increasingly high labour costs have finally taken their toll,” he notes.
There is evidence of his penchant for memorable phrases, a tendency that, deployed in his final valedictory on leaving Rome in 2006, prompted the foreign office to end the practice of ambassadors signing off with parting missives to headquarters in London.
On that occasion, he bemoaned what he saw as a growing managerialism and state of permanent upheaval within the foreign office, prompting him to liken the place to Stalinist Russia and the era of the Cultural Revolution in Mao’s China.
“Can it be,” he asks, “that in wading through the plethora of business plans, capability reviews, skills audits, zero-based reviews . . . we have forgotten what diplomacy is all about?”
In 2003, leaving Dublin, he notes that, despite all the progress in Anglo-Irish relations, “the essential ambivalence of the relationship will remain”.
He continues: “The Irish see nothing contradictory in calling for the Brits out of Ireland while embracing the fortunes of Manchester United, Liverpool and Leeds. ‘Brits out; Manchester United rule’.
“And indeed we’ve had more complaints about [English rugby captain] Martin Johnson’s oafishness in almost literally forcing the Irish president off the red carpet while meeting the Irish team at last weekend’s [Lansdowne Road rugby] international than about the war in Iraq. ”
But, he notes, perhaps optimistically, that “the ancient quarrel is in the process of being solved”.
“What binds the two people together is greater than what separates them,” he writes, “if the Irish will learn to stop scratching at the scabs of history and bury the competition of nationalism. Like that great Irish man of letters, Hubert Butler, I look to the day when the Border on this island becomes a mark of distinction rather than one of division.”