Few investigations have been as comprehensive, damning or politically explosive. The United Nations report into the murder of Rafik Hariri, the former Lebanese Prime Minister, has not only named members of the inner circle in the Syrian Government; it has directly implicated President Assad’s brother-in-law and accused President Lahoud of Lebanon of receiving a telephone call minutes before the killing telling him of the bombers’ plans. The report confirms all the suspicions of Syrians involvement that united most of an outraged Lebanon in demanding Syria’s overdue withdrawal. It upholds the impression of an embattled and floundering Government in Damascus desperate to ward off pressure for change and reform. And it paints a picture of a weak President who either does not know what his intelligence services are doing or cannot control them: a picture, as one diplomat put it, of “a dictatorship without a dictator”.

Syria must now respond to this international indictment of its Government on the charge of premeditated murder. Its first reaction was one of bluster. It denied the charges, accused the West of anti-Syrian propaganda and tried to take comfort in the extraordinary decision to edit out from the report’s final version the names of President Assad’s brother and his brother-in-law, the head of intelligence, who an earlier draft said had “decided to assassinate” Mr Hariri.

What Syria must do is clear. It must turn over for trial the men named. It must allow the UN access to witnesses. And it must stop the attempts to keep its control of Lebanon through violence, intimidation and destabilisation carried out by undercover agents. Already Damascus stands accused of supporting Hezbollah, backing Palestinian opponents of the peace process and giving covert but active support to the terrorist insurgency in Iraq. Promises to close the border and stop the flow of weapons and fighters into Iraq are as empty as they are hypocritical: of the ten insurgents recently killed or captured, all had come through Damascus and at least one had arrived there on a one-way ticket. The chances, however, of Syrian compliance are slim. The arrest of so many top figures would spell the end of the Assad regime. In any case, it is unclear where the suspects should be tried: Syria itself is out of the question; Lebanon, fearful of Syrian retaliation and with a President refusing to resign, is equally ill-suited; and the International Criminal Court does not command the support of the US. The worst thing, however, would be for the UN now to walk away from the case. Lebanese politicians are already terrified that a desperate regime in Damascus would wreak revenge in their country with bombings and assassinations. The UN stood firm against Libya over Lockerbie; it must now be ready to impose sanctions on Syria. The US has made clear that if Mr Assad, like Colonel Gaddafi, shows belated courage in ending support for terrorism and turning over the guilty, he might escape retribution. This is a lifeline to a regime which will collapse under the weight of its internal contradictions.

UN report in full