Normally we would welcome the decision of a prominent figure in public life to talk frankly about coping with a destructive illness like alcoholism. But it would be wrong to describe what Charles Kennedy did yesterday as particularly noble. The admission of the Liberal Democrat leader that he has had an alcohol problem for the past 18 months was forced out of him by imminent revelations in the media. He did not offer it willingly, despite the candid tone he adopted at yesterday's hastily arranged press conference.

And the implications of the revelations are disturbing. Rumours that Mr Kennedy had a drink problem have been around for years. And when these allegations were put to him - including during the past 18 months - he chose to deny them rather than claim that such matters were private. This was not even an evasion; it was a lie. The public have a right to expect they will not be told outright falsehoods by a politician who is asking for their votes.

The admission would seem to explain some of Mr Kennedy's curious behaviour during the last parliament, such as his non-appearance in the House of Commons for the 2004 budget (blamed at the time on a violent stomach bug). We can also perhaps now understand his strange performance at his party's spring conference that same year.

Rather than go quietly, Mr Kennedy has opted for one last throw of the dice. By calling a snap leadership contest and pledging to stand himself he has taken the fight to his growing number of opponents in the parliamentary party.

He is gambling that his popularity with the grass roots membership will see him through this crisis. But even if Mr Kennedy does survive to fight another day - and even if he never drinks another drop of alcohol again - his career as a serious politician would seem to be over.

Mr Kennedy will be remembered as a substantial and popular leader, who delivered the highest number of seats for his party since the days of Lloyd George.

He was also an articulate and persuasive speaker, who provided forceful opposition to the invasion of Iraq. But his inability to raise his party's game before the last election meant that the Liberal Democrats missed their greatest opportunity of advancement in living memory.

One of Mr Kennedy's great strengths has been his rapport with the electorate. When he accused the Prime Minister of having an issue with "trust" it struck home. But now Mr Kennedy has his own trust issue to contend with. This is unfortunate for him and his party. Now both must, surely, look to a future apart.