David Cameron said that at his best Charles Kennedy was the best that politics could be as he lead tributes to the former Liberal Democrat leader in the House of Commons.
Mr Kennedy's ex-wife Sarah and 10-year-old son Donald looked on from one of the side galleries as MPs shared their memories of him.
The Prime Minister also praised Mr Kennedy for the stand he took against the Iraq War, saying it is easy to forget "just what a stand that was".
Mr Cameron said Mr Kennedy's "character and courage inspired us all", adding that there was "something very special" about him.
He said: "Charles Kennedy will be remembered for his success, for his principle and intellect, and above all for his incredible warmth and good humour.
"He had a way of connecting with people, even those who didn't know him well or even at all.
"He was the most human of politicians.
"In the words of Charles Kennedy himself, the vast majority of people think there is a hell of a lot more to life than just politics and you have got to bear that in mind because you are actually trying to represent them.
"At his best, he was the best that politics can be and that is how we should remember him."
Mr Cameron also recounted a number of anecdotes about Mr Kennedy, including a discussion he had with a careers adviser.
Asked what he planned to do with his life, Mr Kennedy answered that he could be a teacher or a journalist, but "if all else failed, there was always politics".
Mr Cameron went on: "So, on his election, his old careers adviser wrote to congratulate him, saying 'I can only presume that all else failed'."
Mr Kennedy's arrival in Westminster was only his third time in London, the Prime Minister told MPs.
The Tory leader added: "Charles Kennedy played a pivotal role in bringing together two parties - the SDP and the Liberals.
"As leader he took the Liberal Democrats to the best electoral result for a third party in British politics for nearly 100 years.
"He told Sue Lawley on Desert Island Discs back in 2003 that his ambition for his party was to find themselves part of a government of the country.
"His achievements laid the foundations for that to happen and, while he was never the greatest fan of the Coalition, and indeed voted against its formation, he never spoke out against the Lib Dem participation in it.
"For as much as he was a man of strong views, he was also a man of great loyalty."
Mr Cameron went on: "At the heart of his political views was a deep commitment to social justice. He passionately believed in Europe as a way of bringing people together, but his most outspoken contribution in recent years was the principled stand he took against the Iraq War.
"Looking back, it is easy to forget just what a stand that was.
"Taking abuse from the major parties on both sides of the House and adopting a position that wasn't even supported by the previous leader of his own party.
"But there was something about the deeply respectful way in which he would conduct an argument. He didn't believe in making enemies out of opponents and he didn't - as he put it - waste time just rubbishing everybody else.
"He made friends even with those who disagreed with him. I think that was one of the reasons why he was so liked and widely supported in taking on the personal challenges he faced."
Acting Labour leader Harriet Harman described Mr Kennedy as "the golden boy from the Highlands" who could stand tall among an exceptional generation of Scottish politicians including the likes of Gordon Brown and John Smith.
Ms Harman said: "History will show that he was one of a great generation of Scottish MPs at a time when Scotland gave this House some of the finest politicians of the era.
"Exceptional politicians like John Smith, Donald Dewar, Gordon Brown, Ming Campbell, Robin Cook - he stands tall amongst a Scottish generation who were head and shoulders above their peers.
"I remember when he first came to this House, aged only 23 - the golden boy from the Highlands, he shone in this chamber.
"He was elected so young and it's a tragedy that he has died so young.
"All our thoughts are with his family."
Ms Harman said the former Lib Dem leader showed that being a career politician can be an honourable pursuit.
She spoke of his commitment to his political cause over his personal career, and his deep seriousness and intelligence, yet warm, funny and generous nature.
Finally, Ms Harman paid tribute to Mr Kennedy for opposing the Iraq War but not denigrating those who voted for military action.
She said: "He was an outstanding parliamentarian and dedicated his whole life to politics.
"That is a powerful reminder to all of us that giving your life to politics, being a career politician can be an honourable, not an ignoble thing.
"He took a philosophical approach to the ups and downs of political life.
"Despite the adversity that he faced, he never became bitter because he cared more about his political cause than he did about his personal career.
"He had a deep seriousness of purpose and great intellect but he wore it lightly.
"He could be the most intelligent person in the room but still be warm, funny and generous, which made him convincing and engaging in equal measure."
"He showed you could be in profound disagreement on matters of serious political judgment, while still accepting the good faith of those who take a different view.
"He disagreed with the decision to go to war in Iraq and he was right.
"But he never felt the need to denigrate those of us who got it wrong."
Outgoing Liberal Democrat leader Nick Clegg paid tribute to his predecessor as a "formidable parliamentarian" but said Mr Kennedy had been much more than his politics.
He said: "Much though he was wedded to politics all his life, I think Charles would have wanted to be remembered as a kind and loving father, brother and son first; and an accomplished politician second.
"And my thoughts and condolences are with all his family and friends today."
Mr Clegg spoke of the "enduring humanity" in Mr Kennedy, adding that he was the "polar opposite of a cardboard cut-out, point-scoring party politician".
Mr Clegg reminded the Commons that Mr Kennedy was "very funny" before adding: "His good humour must not obscure the fact that there was a steely courage about him, most memorably on display when he took the principled decision to oppose the Iraq War.
"Charles was often a lone voice in this House, standing up against a consensus in favour of war on all sides.
"The fact that he was proved so spectacularly right is a tribute to his judgment and his intuitive common sense."
The former deputy prime minister said his colleague had remained "unstintingly loyal" despite opposing the decision to enter coalition.
Mr Clegg said: "He had made his views clear at the outset but respected in good faith what his party colleagues were seeking to achieve in Government and provided support and advice every step of the way.
"Which is why it was no surprise when he said, after being challenged about his loyalties after the 2010 election: 'I will go out of this world feet first with my Lib Dem membership card in my pocket'.
"I am just devastated that it has happened so soon."
Introducing the tributes session, Speaker John Bercow described the late Lib Dem leader as "the boy next door of British public life".
He said: "Charles Kennedy spent almost his entire adult life as an MP. He was assuredly at home in this place, yet perhaps happiest beyond it.
"He was a man of deep progressive principle, but a man also blessed with the popular touch.
"He was a good talker but an even better listener.
"Above all, and perhaps most strikingly, Charles had the rare ability to reach out to millions of people of all political persuasions and of none across the country who were untouched by and in many cases actively hostile to politics.
"In this seminal sense, therefore, Charles was the boy next door of British public life - we salute him.
"We honour his memory and we send today our sincere heartfelt and deepest condolences to his family and his friends."
Veteran Conservative Ken Clarke (Rushcliffe) reflected on Mr Kennedy's arrival in the Commons in 1983.
He said: "He was very young. He was a student. He looked like a schoolboy and rapidly people realised that in addition to all these rather striking attributes, he combined it with being highly articulate, very self-confident and capable of addressing this House in a very fluid and eloquent way, with that jokey, relaxed charm which was his very distinctive style.
"He rapidly became, because he was such an unexpected but unique figure, very prominent not only in Parliament but nationally. He looked as though he would have been destined for a brilliant national career apart from the limited expectations of the Social Democrats and the Liberal Party with which he then associated himself.
"He did actually achieve a good national career and he eventually took his party to heights that would have been unimaginable electorally when he first arrived."
Mr Clarke quipped: "I'm glad to say he was one of the last of that great tradition which said you should best address political problems in an atmosphere of a smoke-filled room, which has been lost today."
Father of the House Sir Gerald Kaufman said: "He had very, very strong views but he was never vindictive. He was never malevolent in expanding those views, he knew where he stood, he worked out where he should stand and you knew when Charles spoke he thought it out, he thought it through, and at the same time you would not budge him unless you could argue him out of a position.
"It's been mentioned again and again, rightly so, that he opposed the Iraq War. And it's been mentioned again that was not an easy thing to do at the time and was not the view of the overwhelming majority of the House of Commons at that time.
"But you would not budge Charles if he worked out a position and he believed that position to be right."
Angus Robertson, leader of the SNP's Westminster group, said: "Politics is a very hard business and while I and my colleagues are delighted the SNP won the constituency of Ross, Skye and Lochaber, I was genuinely saddened Charles Kennedy would no longer be in Parliament.
"It's a mark of the man that when I got in touch with him after the general election, he readily agreed to meet up and share his experience of his leadership of the Liberal Democrats when that was the third party in the House of Commons.
"People across politics will attest to the generosity of spirit that Charles Kennedy showed to people on all sides of the party divide."
He added: "Charles Kennedy was a giant in Scottish and in UK politics."
The SNP's Ian Blackford, who beat Mr Kennedy to take his Ross, Skye and Lochaber seat at the general election, said the former Lib Dem leader lost due to the the Nats' surge across Scotland.
Mr Blackford said of Mr Kennedy's first election victory: "The stories around Ross, Skye and Lochaber are still legendary - of the campaigning that took place in that period back in 1983.
"Charles, travelling around the constituency with his father, his father playing the fiddle.
"And what truly happened in that election campaign is that Charles charmed the constituents, just as he did when he came into this House, when he burst on to the political scene and became a big figure, not just in Scotland but on the world stage as the leader that he became of the Liberal Democrats.
"He loved campaigning and indeed he still loved campaigning as we all saw in the recent general election campaign.
"His desire to appear in front of the electorate, both in terms of his own public meetings and the hustings, and that debating style that has been referred to by so many.
"And it was an absolute privilege to campaign against him.
"And I would say that when I look at the strength of our own benches here today, with 56 members of the Scottish National Party being elected, it was truly the national tide that meant that Charles lost the seat of Ross, Skye and Lochaber."
Veteran Tory Sir Edward Leigh (Gainsborough), who was elected to the Commons in the same 1983 intake as Mr Kennedy, said he believed the pair were "soulmates".
He said: "For all those 32 years that I served with him in this House and on the Council of Europe, of course I was always a political opponent, but in a way I always felt that we were soulmates.
"And sometimes he had to go against the groove and I had to, but there was something there very powerful.
"I think his faith was very powerful, and I like to think that in some previous life he and I might have marched together in some hopeless Highland cause, perhaps as Jacobites, I don't know."
"But his causes were never hopeless and I think his legacy will live on."
Sir Edward also revealed that he voted with Mr Kennedy and opposed the Iraq War, saying his argument was more powerful than simply positioning the Lib Dems as a radical alternative to Labour.
"It's been said, for instance, on the Iraq War that he wanted to place his party as a radical alternative to Labour but I think it went much deeper than that, and was more powerful.
"Mr (Ken) Clarke and myself wouldn't have listened to his arguments and followed him into his lobby if we hadn't been convinced by what he was saying - that there were limits to liberal imperialism, and that he was a true liberal and understood those limits and understood what a difficult part of the world that is and the difficulties that we have met ever since, so he's been proved right on that."
Sir Edward also said Kennedy was a "gentle patriot" rather than a "narrow minded nationalist" and would have been a powerful advocate of the union/
He said: "I think if he was still here, or if he was in the Lords shortly, he would have been really a very powerful advocate for our union because his was a gentle patriotism, not some narrow minded nationalism.
"And he would have been very generous also I think in terms of the participation of the Scottish National Party in this place which I think is very important, and we must welcome that participation and recognise that they must take part in all our debates."
Lib Dem leadership contender Norman Lamb described Mr Kennedy as an "immense talent" who had the "extraordinary ability to reach out beyond the narrow confines of his own party".
He said he had an affinity with people outside politics because he spoke in a language they understood and was "never ceasing" in his courtesy.
Mr Lamb, who was Mr Kennedy's parliamentary private secretary from 2003/05, went on: "He never lost his temper in dealing with people. He was always polite. He used the power of argument to win his case."
He said three things in particular struck him about Mr Kennedy - his "courageous stand" on the Iraq War, his internationalism and "complete commitment" to social justice.
He added: "We must do everything we can, united together, to ensure Charles's legacy, to rebuild the Liberal voice in this country."
Mr Lamb also spoke about the continuing stigma around mental health and addiction, adding: "We, all of us here and beyond, still have a lot to learn in how we combat that stigma and treat it as a genuine illness and offer help to the individual as much as we possibly can."
Another leadership contender, Tim Farron, said Mr Kennedy was primarily concerned about the well-being of others and was successful because he was always himself.
He added: "What he was so good at was his ability to communicate and get to people.
"People say Charles Kennedy was human - yes, he was, but he wasn't contrived.
"He was a persuader and he was a persuader because he was able to reach people in their gut.
"Charles was successful because he was himself, and my advice, I guess, to any of you, if you are ever invited on Have I Got New For You - say no unless you want to be made out to be a prat or unless you are Charles Kennedy."
Praising his stance on the Iraq War, Mr Farron said: "He was surrounded by people baying at him, as if he was somehow Chamberlain, that he was somehow an appeaser.
"Charles Kennedy was principled and he changed people's minds and he was right. He was human, he was principled and he was effective."
Directing his final remarks to Donald looking on, he concluded: "You should be really proud of your daddy, I am proud of your daddy. I loved him to bits and I am proud to call him my friend. God rest you, Charlie."