Updated on 26 August 2009

By Channel 4 News

US President Obama says he is heartbroken to hear of the death of Senator Ted Kennedy, the last surviving brother of president John F Kennedy, who died at the age of 77.

He was the most influential and longest-serving senator in American politics, serving representing Massachusetts in the Senate for 47 years from 1962.

He became the head of America’s most-influential political family following the assassinations of his brothers president John F Kennedy in 1963 and senator Robert F Kennedy in 1968.

But his own political rise was affected by the ‘Chappaquiddick incident’, where a car he was driving plunged into a pond, killing Mary Jo Kopechne who was a former member of Robert F. Kennedy’s staff.

Kennedy swam to safety but did not report the incident to the police until after the woman’s body was found.

He later pleaded guilty to leaving the scene of an accident after causing injury and was given a suspended sentence.

In 1980, he made his only bid to become president by taking on the incumbent Jimmy Carter in the Democratic primaries, but he later withdrew from the battle.

Until his death, Kennedy remained an influential player in American politics, endorsing Barack Obama’s campaign for the Democratic nomination for president in 2008. He collapsed at a lunch thrown as part of Obama’s inauguration as president months later.

Obama said on Wednesday he was heartbroken to hear of the death of Kennedy, a crucial supporter of his presidential candidacy.

“I valued his wise counsel in the Senate, where, regardless of the swirl of events, he always had time for a new colleague,” said Obama.

“I cherished his confidence and momentous support in my race for the presidency. And even as he waged a valiant struggle with a mortal illness, I’ve profited as president from his encouragement and wisdom.”

Kennedy has been described as the American who made the single greatest contirbution to efforts to solve the Northern Ireland problem.

Alex Attwood, a Social Democratic and Labour Party member of the Stormont Assembly, said: “I think his death is a great loss.

“He made a huge contribution to the North, the single greatest contribution of any American politician of recent times, including Clinton.”

Gordon Brown led the British tributes. He 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.”