London (CNN) -- It's not unusual for a visiting head of state to lay a wreath at the Tomb of the Unknown Warrior in London's Westminster Abbey -- but when it happens on Tuesday, the gesture will be anything but routine. This is history in the making. The commemoration by the President of Ireland, Michael D. Higgins, will take place during the first state visit by an Irish leader to the United Kingdom. It follows on from Queen Elizabeth's trip to Dublin in May 2011, the first by a British monarch to the republic since it gained independence from London in 1921. The countries are close neighbors but have a long, contentious, often violent history which has left thousands dead, among them Lord Mountbatten, a relative of the Queen who was killed by an Irish Republican Army (IRA) bomb in 1979. The very fact that the British and the Irish once fought with each other under the same flag is still very difficult for many Irish Republicans to stomach. But the relationship between the two countries has gradually normalized since the peace process of the 1990s. That will be formally acknowledged when Higgins pays his respects at the tomb of an unknown British soldier who died during World War One when Ireland was under British rule. Diplomats from both countries are stressing the significance of the five-day trip. Dan Mulhall, the Irish Ambassador to London, has said that Dublin is "now willing to look at the facts of history" rather than shying away from them. Meanwhile a Foreign and Commonwealth Office spokesperson has said that the visit is about acknowledging the past but also "demonstrating that the relationship is moving on and looking to the future." The spokesperson stressed that both state visits are "pivotal moments in our shared history." The Queen's trip nearly three years ago included a visit to Croke Park, a Dublin sports stadium where 14 people were killed by British forces in 1920 during the war of independence. She also spoke in Gaelic during a dinner in Dublin to audible gasps in the room; and visited Northern Ireland in June 2012, when she shook hands with former IRA commander Martin McGuinness, now the province's deputy first minister. These were all highly symbolic moments that politicians couldn't create to the same effect -- and Buckingham Palace is well aware of that. A palace spokesperson said last month that the Queen herself has become a symbol of the warming relationship between the two countries. The significance of this week's state visit will be further underlined by the presence of McGuinness at a reception hosted by the Queen on Thursday afternoon at Windsor Castle - a move unthinkable only a decade ago. The palace spokesperson confirmed that the Queen is heavily invested in the state visit and that it is personal for her, adding that "the Queen is across every detail." Expect the Irish President to have everything laid on for him, with all the pomp and ceremony that the royal household can muster. Tensions still remain in Northern Ireland: while the bloodshed of previous decades has largely stopped there are still occasional incidents which pose a threat to life and tensions remain between the communities. But Anglo-Irish relations are improving with each symbolic moment -- and this week's state visit is as symbolic as it gets. READ: Mary Robinson: Finally, Britain and Ireland are reconciled .
Visit of Irish president marks first state trip to London since 1921 .
Queen Elizabeth made historic visit to Dublin nearly three years ago .
Foster: Relations between two countries have gradually normalized since 1990s .
London (CNN) -- It's not unusual for a visiting head of state to lay a wreath at the Tomb of the Unknown Warrior in London's Westminster Abbey -- but when it happens on Tuesday, the gesture will be anything but routine. This is history in the making. The commemoration by the President of Ireland, Michael D. Higgins, will take place during the first state visit by an Irish leader to the United Kingdom. It follows on from Queen Elizabeth's trip to Dublin in May 2011, the first by a British monarch to the republic since it gained independence from London in 1921. The countries are close neighbors but have a long, contentious, often violent history which has left thousands dead, among them Lord Mountbatten, a relative of the Queen who was killed by an Irish Republican Army (IRA) bomb in 1979. The very fact that the British and the Irish once fought with each other under the same flag is still very difficult for many Irish Republicans to stomach. But the relationship between the two countries has gradually normalized since the peace process of the 1990s. That will be formally acknowledged when Higgins pays his respects at the tomb of an unknown British soldier who died during World War One when Ireland was under British rule. Diplomats from both countries are stressing the significance of the five-day trip. Dan Mulhall, the Irish Ambassador to London, has said that Dublin is "now willing to look at the facts of history" rather than shying away from them. Meanwhile a Foreign and Commonwealth Office spokesperson has said that the visit is about acknowledging the past but also "demonstrating that the relationship is moving on and looking to the future." The spokesperson stressed that both state visits are "pivotal moments in our shared history." The Queen's trip nearly three years ago included a visit to Croke Park, a Dublin sports stadium where 14 people were killed by British forces in 1920 during the war of independence. She also spoke in Gaelic during a dinner in Dublin to audible gasps in the room; and visited Northern Ireland in June 2012, when she shook hands with former IRA commander Martin McGuinness, now the province's deputy first minister. These were all highly symbolic moments that politicians couldn't create to the same effect -- and Buckingham Palace is well aware of that. A palace spokesperson said last month that the Queen herself has become a symbol of the warming relationship between the two countries. The significance of this week's state visit will be further underlined by the presence of McGuinness at a reception hosted by the Queen on Thursday afternoon at Windsor Castle - a move unthinkable only a decade ago. The palace spokesperson confirmed that the Queen is heavily invested in the state visit and that it is personal for her, adding that "the Queen is across every detail." Expect the Irish President to have everything laid on for him, with all the pomp and ceremony that the royal household can muster. Tensions still remain in Northern Ireland: while the bloodshed of previous decades has largely stopped there are still occasional incidents which pose a threat to life and tensions remain between the communities. But Anglo-Irish relations are improving with each symbolic moment -- and this week's state visit is as symbolic as it gets. READ: Mary Robinson: Finally, Britain and Ireland are reconciled .
during the first state visit by an Irish leader Elizabeth's trip to Dublin in May 2011, the first has gradually normalized since the peace process history." The Queen's trip nearly three years ago warming relationship between the two countries.