Michael D Higgins flies to London ahead of historic state visit
The President of Ireland, Michael D Higgins, has arrived in London ahead of the start of the first state visit by an Irish head of state.
The president and his wife, Sabina, will be the guests of the Queen and the Duke of Edinburgh at Windsor Castle for the four-day visit.
The trip officially begins on Tuesday.
In May 2011, the Queen became the first British monarch to visit the Republic of Ireland.
Both British and Irish sources stress that relations between the two countries are extremely warm, especially after the Queen's historic state visit to the Republic of Ireland.
Northern Ireland's deputy first minister, Martin McGuinness, who did not meet the British monarch during her Dublin visit, will be present for the state banquet, along with amongst others, First Minister Peter Robinson, Prime Minister David Cameron and Taoiseach (Irish prime minister) Enda Kenny.
State visits follow a certain protocol: apart from meetings with the Queen and senior politicians, they include an address to Parliament, laying a wreath at the tomb of the unknown soldier and a state banquet as well as another banquet in the City of London.
President Higgins will also meet members of the Irish community living and working in Britain, including those who work in the NHS.
There will also be a strong emphasis on the cultural links between the two countries; the president will attend a celebration of Irish culture and arts at the Royal Albert Hall and will visit William Shakespeare's Stratford-on-Avon on Friday before returning to Dublin.
One of the lighter moments may well be on Wednesday morning at Windsor Castle when Domhnall, the Irish Guards' Regimental mascot, a wolfhound, will be presented with a new dog coat.
Both British and Irish sources say the Queen has taken a very keen personal interest in the details of the visit after her own state visit which was so well-received in the Republic of Ireland, when she bowed in memory of those Irish men and women who had fought against the crown and her ancestors in the fight for Irish freedom.
She was widely seen as striking the right note in acknowledging the difficult past between the two states and the current warmer relationship, which Enda Kenny has called "a golden age".
The peace process and devolution has normalised relationships between the United Kingdom and the state, constitutionally known as Ireland.
As happened three years ago, there will be a lot of talk about the close family ties across the Irish Sea and the strong trade and cultural links.
While the Queen's state visit was undoubtedly historically more important, this week's return visit is in its own way very significant.