By Brian Wheeler
BBC News politics reporter
When they elected Charles Kennedy as their leader in 1999, the Liberal Democrats knew they had chosen a "bon viveur" over rivals with more gravitas but less charisma.
Mr Kennedy has appeared on the BBC's Have I Got News for You
Mr Kennedy was a genial, witty figure more than capable of holding his own on television panel games such as Have I Got News for You.
He was described in profiles as "lightweight" and "a charmer", whose laid-back approach contrasted with more earnest, policy-heavy rivals such as Simon Hughes and Malcolm Bruce.
He was also known to be fond of a drink - he described himself during the leadership contest as an "up front social drinker" - and his claim to be trying to give up smoking was already becoming a familiar refrain.
Rivals accused him of laziness - one dubbed him "inaction man" compared to his ex-marine predecessor Paddy Ashdown.
It was even suggested in 1994 that he failed to take politics seriously when he won £2,000 from a £50 flutter betting that the Lib Dems would take only two seats in the European elections.
But Mr Kennedy never seemed worried by such criticism. He knew he was a popular figure among ordinary party members - and his blokeish image won him votes from people normally turned off by politicians.
He also took his politics seriously, had a sharp tactical brain and extensive front rank experience. He was only 39 when he became leader - but he had already been an MP for 16 years and had served in a succession of frontbench roles.
Here is the story of his life in politics.
THE EARLY YEARS
Mr Kennedy was born in Inverness and grew up in a remote crofter's cottage in the Highlands. He was educated at Lochaber High School - where at 15 he joined the Labour Party - and Glasgow University.
His father Ian says his son's attitude at school was: "Do enough to get by without knocking your pan in."
Charles harboured political ambitions from an early age
This reputation for a laid-back approach to life persisted at university, where his nickname was "Taxi Kennedy" for his habit of taking a minicab for the quarter mile journey from the union buildings to his lectures.
But the young Kennedy also had political ambitions, joining the Dialectic Society, a debating society, and becoming president of the union in 1980 and joining the Social Democratic Party (SDP).
He won an honours degree and a Fulbright scholarship to Indiana University in the US, where he worked on a thesis on Roy Jenkins. He seemed set for a career in academia - before agreeing to fight the seemingly no-hope seat of Ross Cromarty and Skye for the SDP at the 1983 election.
Mr Kennedy had thought his chances of victory in Ross Cromarty and Skye so slim he had flown back to the US when the polls closed.
Mr Kennedy had his sights set on a long political career
But he unseated government minister Hamish Gray and - instead of returning to academia - found himself thrust into the world of Westminster politics at the tender age of 23, as the youngest MP.
At first he was SDP spokesman on social security, Scotland and health and when most of his party merged with the Liberals to form the Lib Dems in 1988, he continued to hold a series of frontbench posts.
He made his first major breakthrough in 1990 when he was elected to the crucial post of party president.
During the 1990s, Mr Kennedy built his profile through TV appearances, earning him the nickname - which he hated - of "Chatshow Charlie".
In 1999, he beat off five competitors to take over as party leader, gaining 28,425 votes to second place Simon Hughes' 21,833.
Mr Kennedy at a party rally in 2000
He said he wanted to make the Liberal Democrats a party of government, by building its strength on local councils and in the devolved administrations of Scotland and Wales.
On the national stage, he pledged to form policies that would appeal to both Conservative and Labour voters.
BREAK WITH LABOUR
Mr Kennedy supported predecessor Paddy Ashdown's attempts to form an alliance with the Labour Party, based around a shared commitment to electoral reform and Europe.
Kennedy uncoupled his party from Labour, in contrast to Paddy Ashdown
But as soon as he became leader he set about uncoupling the party from Labour, forming distinctive policies on taxation, the environment and, as Labour's enthusiasm for the single currency cooled, Europe.
At the 2001 general election the party improved its share of the vote to 18.3%, 1.5% more than in the 1997 election.
Although smaller than the 25.4% share the SDP/Liberal Alliance achieved in 1983, the Lib Dems won 52 seats compared to the Alliance's 23.
The birth of his first son Donald brought Mr Kennedy enormous joy
Mr Kennedy's 2002 marriage to Camelot public relations executive Sarah Gurling - party finance chief Lord Razzall was best man - was seen by many in the party as a sign he was settling down.
The birth of his son in 2005 was seen as a further sign that the hard-partying Kennedy - one commentator had dubbed him "Jock the lad" - was being transformed into a family man.
Many think Mr Kennedy's finest political hour was his decision to oppose the 2003 US-led invasion of Iraq.
It was a decision he had agonised over and he backed British troops once the invasion was under way.
But in the run-up to the war Mr Kennedy became the unofficial leader of the anti-war movement - and the main voice of opposition in the Commons.
Mr Kennedy said his opposition to Iraq was 'principled'
It was seen by many as a principled stand that was borne out by events when it turned out the intelligence suggesting Saddam Hussein had weapons of mass destruction had been wrong.
It attracted support from Conservative and Labour voters disaffected by their parties' support for the war.
Liberal Democrats fully expected to reap the electoral rewards at the 2005 general election.
RECORD ELECTION RESULT
Mr Kennedy fought the 2005 election as "The Real Alternative", attempting to pull off the difficult task of appealing to both Labour and Tory voters.
The party was rewarded with 62 seats - its highest tally since the 1920s.
The Liberal Democrats made election history in 2005
But there was a feeling of deflation among some MPs - particularly some of the recent intake on the right of the party who were impatient for power.
The party's 2005 autumn conference was billed as a "celebration" of electoral gains - but ended with Mr Kennedy battling to silence growing criticism of his leadership.
Mr Kennedy was a familiar sight in the bars and clubs of Westminster for more than 20 years and was known to be fond of a drink.
But whenever he was asked whether he had a problem, he flatly denied it.
Talk of Mr Kennedy's drinking grew steadily
After he became the leader, the first time the question of Mr Kennedy's drinking became a mainstream issue was after a 2002 interview with Newsnight's Jeremy Paxman.
"How much do you drink?" Mr Paxman asked. "Moderately, socially, as you well know," was the reply.
Paxman: "You don't drink privately?"
Kennedy: "What do you mean, privately?"
Paxman: "By yourself, a bottle of whisky late at night?"
Kennedy: "No, I do not, no."
Mr Kennedy made several more polite but firm denials over the next few years, sometimes adding a pledge to quit smoking.
In 2004, he said he had cut down on his drinking and was taking more exercise - now it has emerged he was receiving treatment for an alcohol problem.
Despite the public denials, it seems efforts were going on behind the scenes to encourage Mr Kennedy face up to his demons.
Four top party figures apparently cornered Mr Kennedy in his private office in 2004, and insisted he acknowledge his drink problem.
According to reports, they succeeded in persuading him to admit his condition, and he has since been receiving "private" medical help.
Colleagues in the party apparently expected Mr Kennedy to stand down after the general election in May.
At the 2005 Lib Dem conference there were rumours
During the campaign he seemed to have trouble answering media questions on some policy details, which he blamed on the birth of his first son but which others put down to his drinking.
He did not resign, and later heightened concerns in November by pulling out of a scheduled visit to Newcastle while en route.
It followed the 2004 Budget speech, when Vince Cable and Sir Menzies Campbell were reportedly forced to stand in for him at 15 minutes notice. He denied his absence was drink-related.
Mr Kennedy's perspiring performance at the 2004 spring conference - put down to a stomach bug - also sparked rumours of alcohol abuse.
The election of David Cameron as Conservative leader - and his subsequent appeal to Lib Dem members to jump ship - appeared to throw Mr Kennedy's colleagues into near panic.
They feared the party lacked direction and dynamism, compared to the revitalised Tories.
Senior figures such as deputy leader Sir Menzies Campbell and Simon Hughes told Mr Kennedy he had to "raise his game" or face a leadership challenge.
But Mr Kennedy might just have weathered the storm had it not been for journalists from ITV News confronting him with evidence - supplied by senior party colleagues - that Mr Kennedy had received treatment for alcohol addiction.
In the end, Mr Kennedy was left with no option but to resign
Within an hour of being confronted with detailed allegations, Mr Kennedy made an extraordinary personal statement at party headquarters in Westminster, admitting he had a drink problem.
He threw himself on the mercy of the party membership - among whom he has always been very popular - announcing a leadership contest he intended to take part in.
But his gamble failed to pay off as frontbench figures broke cover to say he should not take part in the leadership contest. More than half of his MPs were openly urging him to quit.
Faced with the threat of a mass walkout by his frontbench team Mr Kennedy felt he had no option but to resign.