Whatever UN inspectors find as they visit the sites of last week’s disputed chemical weapons attacks in the suburbs of Damascus, a western strike on Syrian military assets seems increasingly likely. Bashar al-Assad has prevented any inspection long enough to ensure much of the evidence is likely to have been tainted or even evaporated. Washington is right to dismiss the regime’s acceptance of UN inspectors as too little, too late.

Mr Assad’s battle to hold on to power at any cost – including the lives of some 100,000 Syrians – is founded on the assumption the international community is too divided to act with conviction. He has exploited the divisions to take the war on his own people to terrifying extremes. Syria’s president will be gambling that allowing the inspectors in will deepen divisions over the appropriate response to his apparent use of weapons of mass destruction. But this is a gamble he cannot be allowed to win.

Of course the inspectors have to be given a chance to assess the situation. But they should be clear very quickly whether they believe the evidence has been compromised. That chemical weapons were used seems all but certain. The weight of evidence also points to culpability of the Assad regime. It controls enormous stockpiles of chemical weapons, has the military capability to deploy them, and was conducting an offensive in the area on the day of the attack. Fragmented and ill-equipped rebel forces do not have the resources for such an offensive.