'We got him" was the cry. "A great day" the assessment. May 2011? Well yes, but also December 2003, after the capture of Saddam Hussein. The years immediately after the capture of Saddam were anything but great. They were awful, with terrorism on an unprecedented scale in Iraq led by one of Osama bin Laden's most fanatical followers, Abu Musab al Zarqawi, whose speciality seemed to be beheading Western captives.
So despite the understandable sense of euphoria, satisfaction and (for the relatives of those killed in their thousands on Bin Laden's instructions) closure, let us temper our relief with a realistic assessment of the future of Islamic terrorism, of which al-Qaeda is the leading but hardly the only brand name.
Part of the difficulty arises precisely from the fact that al-Qaeda is now a franchise as well as, apparently, a calling, which brings together a variety of militant jihadi organisations and movements.
After al-Qaeda in Iraq (aka al-Qaeda in Mesopotamia), we have had al-Qaeda in the Islamic Maghreb (AQIM), al-Qaeda in the Arabian Peninsula (an amalgamation of the two Yemen and Saudi branches) and al Shabab, the Somali rebel group, which has stated that it is aligned "with the international jihad led by the al-Qaeda network", as well as an ever-more intimate and troubling relationship between AQIM and Boko Haram, a militant Islamist group in Nigeria.
So while the fragmentation of al-Qaeda may suggest weakness, it is also a strength, as each variant has its own specific agenda as well as a more general one and is unlikely to be penetrated by outside intelligence operatives or compromised by the capture of the al-Qaeda leader's computers. al-Qaeda is also closely linked with the Taliban in Afghanistan and Pakistan and groups in Indonesia and other distant centres of Islamism.
Several of these groups have vowed vengeance for Bin Laden's killing. Jihadi websites talk of "a thousand Bin Ladens being born today". On the other side of the war on terror, the Obama administration has promised to crush al-Qaeda as though it now had the organisation on the run or in its death throes.
A more realistic assessment might be that while major acts of terror on the scale of 9/11 might be unlikely -- al-Qaeda is definitely weaker now than it was 10 years ago -- Bin Laden, while alive, remained an iconic, charismatic figure who is now morphing into a martyr and who may yet from beyond the grave radicalise and inspire a new generation of Islamist activists.
The recent decision by the White House not to release pictures of his body was well founded. Some acts of reprisal would seem almost inevitable. So Western leaders are right to counsel extreme vigilance. But al-Qaeda, its subsidiaries and Islamic terrorism are not going to disappear overnight. And while a decentralised organisation may not have the capacity to launch spectaculars like the Twin Towers attack, it can still mount murderous attacks on Westerners such as the one in Marrakesh, killing 16 people, mainly foreign tourists, a few days ago.
The root causes of its antagonism to the West and western culture, its anger at Western boots polluting the soil of Islam, its frustration at the impasse over the Arab-Israel or Palestinian question, will remain. The toxin may be diluted when the last US/UK and other Nato soldiers have left Afghanistan, but Islamism has a broad agenda -- at the same time calling for a pan-Islamic political entity and for the destruction of any Western presence or influence in the Muslim world.
Given such all-encompassing objectives and the mass indoctrination of thousands of poor, impressionable young Muslim boys and men in richly endowed madrassas, it would be a pipe dream to imagine that jihadists are going to be beaten militarily or ideologically any time soon.
Major questions remain, of course, about Pakistan's role or non-role in the operation. It seems clear that no Pakistani received any notice of the operation until the Seals were out of Pakistani airspace, but had they, as they claim, identified to the US the Bin Laden safe villa as a suspect address?
Hard to believe they knew nothing of it, given the villa's location a couple of hundred yards from Pakistan's equivalent of the Curragh.
Were they kept in ignorance of the planned operation for fear that they might compromise it? Certainly. The Pakistan intelligence organisation (the ISI), credited with creating the Taliban, plays an ambiguous role in the war against terrorism which they regard as no more than a side-show to their undeclared war against their neighbour India over Kashmir.
Lest all this comes over as too gloomy, let's consider some positives. It's hard to take issue with this well-executed operation, clearly mounted on a shoot-to-kill basis, when the man concerned has never regretted for a moment the deaths of thousands of innocent people in New York and elsewhere.
Obama will certainly get a bounce in the polls, to which he is more than entitled. To some extent -- at least in American eyes -- this seemingly perfect operation somehow expiates the still lingering demons haunting Washington since Jimmy Carter's botched operation to rescue US diplomats taken hostage in Tehran by supporters of Ayatollah Khomeini 30 years ago cost him his re-election.
And although there are concerns that the Libyan rebels in Benghazi include some al-Qaeda elements, the headline story from the Arab Spring has been that the revolutions have been spearheaded by progressives who believe in freedom and justice, not oppression and reaction.
While there is a risk that Bin Laden as a martyr figure may galvanise Islamists into attempts to take over the Arab revolution, they are not in tune with the democratic zeitgeist and should be marginalised. It is not just the West that must be vigilant.
Sir Ivor Roberts is president of Trinity College, Oxford, and a former British ambassador to Ireland, Italy and Yugoslavia.