Tributes were paid to Edward Kennedy in both the UK and Ireland today.
Prime Minister Gordon Brown led UK tributes to Senator Edward Kennedy, saying he would be mourned in "every continent".
Mr Brown praised the senator for "fighting for the causes which were his life's work" even as he faced illness and death.
Politicians lined up to pay tribute to Mr Kennedy following the announcement from his family today that the 77-year-old senator, who was diagnosed with a malignant brain tumour last year, had died.
Mr Brown said: "Senator Edward Kennedy will be mourned not just in America but in every continent.
"He is admired around the world as the senator of senators.
"He led the world in championing children's education and health care, and believed that every single child should have the chance to realise their potential to the full.
"Even facing illness and death,, he never stopped fighting for the causes which were his life's work.
"I am proud to have counted him as a friend and proud that the United Kingdom recognised his service earlier this year with the award of an honorary knighthood."
He added: "My thoughts and those of Sarah are with his remarkable and loving wife Vicki and his great family."
Irish Taoiseach Brian Cowen said Mr Kennedy will be remembered with great affection and enduring respect.
"Throughout his long and distinguished career in politics, Ted Kennedy has been a great friend of Ireland," Mr Cowen said.
"He has used his considerable influence in the world's most powerful parliament for the betterment of this island.
"In good days and bad, Ted Kennedy worked valiantly for the cause of peace on this island.
"He played a particularly important role in the formative days of the Northern Ireland peace process in the early to mid-1990s. He has also always been a strong advocate of US investment in Ireland."
Mr Cowen described Mr Kennedy as one of the most distinguished and talented figures in American politics. He said he made a massive contribution to his country and to the causes of justice and peace around the world.
He was a great champion of the vulnerable and the less well-off in American society .
Mr Cowen added: "America has lost a great and respected statesman and Ireland has lost a longstanding and true friend."
In Northern Ireland, Democratic Unionist Party MP Jeffrey Donaldson said that in his latter years Mr Kennedy had come to realise that some of the pro-republican stances he took in the earlier years of the Troubles had been unhelpful.
The Lagan Valley MP said the party was sorry to learn of Mr Kennedy's death and said he was someone they had come to know quite well over the past 20 years because of his involvement in the peace process.
He said: "There is no doubt Senator Kennedy very heavily favoured the position of Irish Republicans and at times his interventions in Northern Ireland were deeply unhelpful."
But he said: "I think Ted Kennedy came to understand that the situation in Northern Ireland was much more complex than the simple notions that had been put into his head by republican propaganda.
"As the years passed, he did moderate his position somewhat and in the end he realised some of the stances he had earlier taken were not helpful."
Former foreign secretary Lord Owen said he admired Mr Kennedy's resurrection of his political career after Chappaquiddick.
"He came back and in the Senate became - I think it would be accepted - the most influential senator on all sides," Lord Owen told BBC Radio 4's Today programme.
"It will be very interesting now to see how the Senate responds to his death. It's a very emotional place and there will, of course, be this very important health reform legislation coming back in September and in my view we will see Kennedy's influence even beyond death on the Senate."
Lord Owen said he was "not sure" whether Mr Kennedy would have ever been president, even without Chappaquiddick.
"I somehow think that Teddy Kennedy, in that respect, major office of president, was a flawed character and I don't think he would have ever made it, personally," he said.
"He did have a drink problem for quite a long while."
But he paid tribute to Mr Kennedy's role in the Northern Ireland peace process.
"His influence on the peace process and his influence on successive American presidents was absolutely crucial and in particular, of course, on President Clinton," Lord Owen said.
"All the time, behind the scenes, Teddy Kennedy was using his influence and I think we in this country have a huge personal debt to him on Northern Ireland."
SDLP leader Mark Durkan worked as an intern for Mr Kennedy in 1985 and described him as "absolutely inspirational".
He said Mr Kennedy had helped many people in the US overcome their prejudices and preconceptions about the Northern Ireland situation.
"He made himself available to everyone in the Northern Ireland political scene.
"He was someone who, more than anyone else, established the validity and benevolence of the American interest and how positive the Irish-American interest in our situation could be - that it didn't have to be just pro-nationalist, didn't have to be anti-unionist, it was about helping make sure there would be a process with a democratic outcome in which everyone could share the benefits."
Mr Kennedy, he said, used his position not just to influence politicians in Congress but also in the White House to become positively engaged in Northern Ireland.
Many of Mr Kennedy's staff went and worked for President Bill Clinton on the Irish issue, he said.
US ambassador to Ireland Daniel Rooney, a friend of the late senator, also praised his role in the peace process.
"Senator Kennedy was not only a great American statesman, but also a great friend of mine and all the island of Ireland and its people," the ambassador said.
"A member of the 'Four Horsemen', he was instrumental in advancing the historic ceasefire in 1994, and he contributed to the talks that brought peace.
"In the Senate, he introduced resolutions condemning all violence in Northern Ireland and expressing support for the Good Friday Agreement of 1998 as the blueprint for lasting peace in Northern Ireland."
Mr Kennedy was one of four influential Irish-American politicians - nicknamed the Four Horsemen - who lobbied for peace and economic growth on both sides of the Irish border.
Former deputy prime minister John Prescott, who worked with Mr Kennedy on a number of defence committees, said: "Kennedy was a great politician, he was the traditional liberal democrat who always wanted to make things better.
"I respected him greatly. It's a sad day generally for democracy and progressive ideas."Reuse content