There are few, if any, contemporary politicians who are naturally as sharp, articulate and entertaining as Charles Kennedy. It is something of a national loss, therefore, that the precocious 23-year-old who promised so much when he arrived in the House of Commons should be languishing on its back benches 23 years later. The extracts that we publish today and tomorrow from Charles Kennedy: A Tragic Flaw, a biography by Greg Hurst, our political correspondent, explain vividly how and why the prodigy fell to earth. They also suggest that he has a mountain to climb if he wishes to return to frontline politics.

The book’s revelations should settle any lingering doubts about whether Mr Kennedy was treated harshly when senior colleagues decided eight months ago that he was unfit to lead their party. The impression he gave then, that he had begun recently to receive medical help for a drinking problem, was misleading. He had been receiving it for four years. That he had decided in 2003 to come clean about his alcoholism, only to change his mind, shows that the party had been in the unsteadiest of hands for too long.

The disclosures will make difficult reading for Liberal Democrats. They are entitled to feel queasy that they were being led through at least one general election, the Iraq war and other pivotal events by a figure whose, largely secret, drinking made him unreliable. That his public performances were growing increasingly erratic was at least visible. Galling to party members will be the level of complicity and denial of Mr Kennedy’s inner circle. They doubtless believed that in lying for so long about their leader’s state of physical and mental health they were acting in the best interests of the party. In this they were mistaken. Consistently and habitually misleading journalists, party members and voters constituted a significant breach of faith that will take time to repair, particularly while some of those responsible remain senior figures in the party.

The reputation of Sir Menzies Campbell may require tweaking in some people’s eyes. Dubbed “Ming the Merciless” for the way he was perceived to have manoeuvred against Mr Kennedy earlier this year, a fuller assessment suggests a moniker nearer the mark might be “Ming the Merciful”. Privy to Mr Kennedy’s secret since 2003, when he was summoned to attend the planned public confession, he could have made life intolerable for his leader. He did not. But was this the right course of action? Where some will be inclined to see benevolent discretion, others may detect a failure to deal with the problem that was threatening his party, a lack of mettle.

Neither Mr Kennedy’s drink problem nor the way he tried to hide it is uncommon, and he deserves some sympathy for his travails. Given his past ambiguities about his health, though, the judgment about whether he can make a telling contribution to Liberal Democrat and British politics will be necessarily dispassionate. For instance, when he went public with his alcoholism, he said that he had not had a drink for two months, “and I don’t intend to in the future”. Has he succeeded or slipped? His political future is not necessarily contingent on what answer he gives. But his credibility does depend on answering such inevitable inquiries with clarity and honesty. Otherwise further chapters may need to be written on Kennedy’s tragic flaw.