Sceptics have since spoken quizzically of that amazing week of mourning after her death - when the most heterogeneous crowds spontaneously congregated on London's streets and appropriated the parks and public places. To the cynics, the absence of public memorialising today merely confirms that the Diana effect was shallow, a sentimental spasm of embarrassing excess. It meant nothing because it changed nothing. See, she's forgotten already! But the very expectation that the people would feel driven to repeat their performance of public mourning is to misunderstand their manners and motives.
There is no Diana effect because Diana is dead. It was not the princess who produced those quiet, contemplative congresses of August and September 1997: it was the people. They had their feelings and they had their say for a week or so, and then it stopped. It was all over.
Yet their improvised memorial, their determination to bear collective witness to her life and death, expressed a confidence and flair for collective feeling that finds little or no articulation in British politics. What seemed to astonish commentators and politicians alike was that the people somehow knew what to do, where to go, and how to have their feelings.
For there was more to it than the national "outpouring of grief" proclaimed by a bemused mass media. It was a time when people did some real thinking about the bad behaviour of Britain's aristocracy, whose protocols were supposed to help them cope in public with personal tragedy but which instead served simply as vehicles to reveal the personal inadequacies of key members of the Royal Family. These same royals were the people who panicked when Diana challenged their power to deceive her, control her and then dispatch her to the loonybin, the Tower or rich but redundant exile. They panicked when the people then made plain their dislike of royalty's disrespect.
If the people knew what to do, no one else did: the Royal Family fought with itself and with its in-laws over everything, from the mortuary to the order of service, from who would walk with the coffin and where or whether to fly their flags. The Government, too, was ambivalent towards the manifestation of public feeling because it, too, recognised the sense of protest that infused the mourning. There was a sub-republican rumbling in the discontent, from which ministers recoiled.
It was in response to this that the Government offered its services to help the Royal Family manage a mess of their own making and one where they could not find an idiom in which to endorse or at least address a public debate which New Labour feared and loathed. Within months it was ineptly affirming the Queen as "the Best of British" at precisely the point when her reputation as a dull but worthy public servant was ruined and she came to be regarded by many of her faithful fans as a horrible old bag. This provided a clue to the resonance of contemporary manifestations of public mourning which have been resolutely minimised by successive governments.
It began after the First World War when millions of people congregated around the elegiac simplicity of the Cenotaph when it was built in Whitehall as a monument to the fallen. No one in power in 1919 had expected the people to take to the streets in such numbers to pay their respects to their lost loved ones and to themselves, the survivors of an international military disaster. Perhaps we still have no measure of that moment, memorialised in every town in these islands by the iconography of men giving away their lives nobly but needlessly.
Then in 1945 the survivors of another world war once more said "never again". They were bearing witness to collective trauma and, more, their lament was a warning. But they too were not taken seriously. For they were not merely making a comment on the horrors of the trenches or of the Holocaust. They were also making a critique of war itself.
That is the point about public grief, from Hillsborough to Dunblane and Omagh: grief is animated both by loss and by outrage. Liverpool's reaction to the disaster at Sheffield's Hillsborough stadium - where their fans died in a needless and mismanaged crush - was both a lament about the city's loss and a political protest. The decision earlier this year to memorialise the Hillsborough disaster, 10 years after the fans died, was a response not just to death but also to the way the dead were maligned by the tabloids and the Sheffield police. It was a statement that the survivors have not secured justice, and a protest against the fact that no one in South Yorkshire police has been held responsible for the systematic doctoring of the police statements made in the aftermath - doctoring designed to minimise police managers' culpability.
The inadequate political reaction to Hillsborough, as to the death of Diana, exposed a failure to read public reaction as anything other than plebeian hysteria. That is because Britain's parliamentary politics no longer feels any responsibility to champion the people, to measure the zeitgeist and give it institutional expression.
If the Government felt that it had consummated its triumph in the general election with Tony Blair's bathetic elegy to Diana, then it was wrong: its silence during the week of mourning revealed a panic about the public feeling and the swell of republican murmuring. It failed to interpret the significance and subtlety of people's response to this woman. Her slow but determined journey to self-discovery, her response to oppression through self-harm, her humiliation by a man who made her service his own ambition for personal and political sovereignty, and her commitment to good causes from Aids to fighting the international trade in land mines all made the ingenue interesting.
If Diana had done nothing else, she had done something no one else had done this century - called the Royal Family to account for their personal politics. She terrified the Establishment not because she was a closet republican - she wasn't, she was one of them - but because she revealed during her Panorama interview that she drew her strength not from them, her own class, nor from the dire men available for love, sex and passion, but from other women. The relationship was reciprocated. After all, no rich and powerful woman had ever talked so eloquently about her humiliation and self-harm.
Even if no government ever thought this was important, the people did. She was neither saint nor heroine, neither republican nor revolutionary, but her life engaged her in themes that constitute a national argument - from the arms trade to sexual politics, to how men do fathering to the meaning of monarchy, personal and political power and accountability. Her own life was part of a conversation in which we are all participants. She may be dead but she is not forgotten, and we are still arguing about these great themes which helped give her life meaning.
Our problem - as the people - is that parliamentary culture no longer, if it ever really did, embraces the great preoccupations that ricochet around civil society. We are having the conversation without champions in either Whitehall or Windsor.