It was the sudden squawking of the Hyde Park geese shattering the breathless hush that told us the cortege was drawing near. The cloudless, azure sky and soft September breeze merely confirmed what many believed; that heaven itself had ordained her flight to the right hand of God.
Now, as her body drew close, the silence deepened, cathedral-like, broken only by the eerie clip of the horses' hooves; the air so tense and still that it seemed the people's hearts had stopped beating.
The single word "Mummy" on a wreath of roses laid across the coffin broke the dam. You didn't have to be a monarchist, or a Hello!-addict or a media-driven hysteric to be moved. For who, stumbling on the funeral of a young mother dead before her time, would not weep at the sight?
An old man saluted; a young girl blew rose petals; a Spanish woman burst into a frenzied: "Ave Maria, plena de grazia. . ."
And then it was gone, the coffin such a little object, dwarfed by the rather fierce-looking mounted police, the black horses of the King's Troop, the bearskin helmets of the expressionless military escort.
Afterwards, when the extraordinary moment had passed, a bewildered woman dabbed a tear: "The coffin seemed so small. . .I can hardly believe it contained that tall, strong, beautiful girl. I can't believe it. . ."
All around her, they nodded sympathetically. As the hoof-beats died away, they exhaled and stood for a moment, blinking in the sunlight. Then, slowly, reluctantly, they turned and joined one of the greatest mass movements the British capital has ever seen, trudging silently past the lake and over the bridge, on towards the two giant television screens in Hyde Park. Some carried flasks, food baskets, rugs and cool boxes but few felt able to speak.
They settled themselves on the grass, squinting against the sunshine, lost in a private world dense with repressed tears and leaden expectation.
But though they were down, they were by no means out. When the gravitas-laden Dimbleby commentary tried filling air-time by describing more festive times in Horseguards Parade - "horses with their bits jangling" - the unwitting double entendre sent a great peal of laughter through the crowd. It marked the beginning of a 90-minute communal, emotional roller-coaster of a kind most of us will probably never experience again.
They watched as old Britain ceded to the new: in the way the old pomp and military precision yielded to 500 representatives of Diana's disparate charities strolling in their casual dress and ragged lines, their modest informality and pain-wracked demeanour a perfect mirror of new Britain, an accusation almost to the Establishment; in the unprecedented way the royals left their palace to stand outside the gates, waiting to bow before Diana's coffin in a levelling of grief; in the way the Union flag fluttered at half-mast above Buckingham Palace, signifying, as nothing else, that the will of the people had prevailed.
As the flag rose, a great mass of people got to its feet and applauded. It rose more tardily for the national anthem; some not at all. "I'm not standing for God Save the Queen," spat a woman, and the crowd around her remained seated. As a verdict on the royal family's desperate damage-limitation exercise on Friday, it was damning.
Even more damning was that by the time the service ended, the new Popular Princess Party had found its spokesman - and he was from within. When Charles Spencer, head of a family from the heart of the English aristocracy, declared in an electrifying roar of loss, love and fury that his sister "needed no royal title to generate her particular magic", the great, grim mass rose as one and applauded with wordless, painful ferocity.
It was not just a slap in the face for the royal family and its vengeful stripping of her HRH status; it illustrated perfectly why those who defended Charles as "at least as devoted to good works as Diana" or Queen Elizabeth as "a grandmother entitled to grieve in private", had missed the point.
The public had long since decided that he and his relations had made a mockery of the marriage and the raw, unsophisticated devotion brought to it by the young, naive Diana; then compounded the insult by freezing her out.
For an outsider talking to ordinary Londoners within 36 hours of her death - long before the royals betrayed the extent of their detachment from modern Britain, or the flower-laying, tear-drenched public grief had begun to feed on itself - it was obvious that the old-style monarchy had long since begun the slow slide from grace.
Charles Spencer merely delivered the coup de grace. Bald and direct as it was, some observers believe that the full implications of his address have yet to be appreciated.
For example, when he expressed his bewilderment about "why her genuinely good intentions were sneered at by the media" and concluded: "It is baffling." Some interpreted this as a barely-masked accusation aimed at senior courtiers - including his brother-in-law - whose powerful tentacles reach deep into the media and who are known to have leaked damaging information about Diana.
In Hyde Park, the people weren't baffled at all. They had made up their minds. The chillingly-precise phrase "we, your blood family", addressed to Diana, caused them to rise again and their applause seared through the heart of London; was echoed by the throngs lining the streets outside Westminster Abbey; and finally, incredibly, was taken up by the invited guests within.
"My lord," gasped a London librarian, "can you believe this? Those people are applauding in Westminster Abbey - the site of the coronation. For the English, this is the equivalent of the storming of the Winter Palace . . ."
Nothing would ever be the same again. These watershed moments were shot through a deeply-affecting tapestry studded with glorious music and words of profound significance for those who craved them and their consolation. Never has language been so carefully noted, analysed and utterly approved of by so many. Nor music so disparate been so captivating to such a broad swathe of tastes.
In the vast, open-air cathedral that Hyde Park had become, many rose, tears trickling down their faces, for one of Diana's favourite girlhood hymns, the one she chose for her wedding, I Vow to Thee My Country, and as soprano Lynne Dawson's Libera me from Verdi's Requiem, soared to the heavens, there were only muffled sobs.
Almost uniquely for a politician, neither Tony Blair's sincerity nor his familiarity with the reading from Corinthians were questioned by the crowd. His emotional tone chimed perfectly with the public mood as he gave meaning to the phrase: For now we see through a glass, darkly but then face to face . . .
"Can't imagine Maggie Thatcher getting away with that somehow. You'd just never be able to believe her, would you?" said a woman.
But if there was a true Diana moment on Saturday, it was when Elton John ran his fingers across the opening chords of his reworked song, Candle in the Wind. Candles flickered, couples clung to each other, grown men sobbed and many bowed their heads.
Goodbye England's rose. . .This torch we'll always carry for our nation's golden child - not unseemly, not tacky, but a powerfully, appropriate farewell from a friend and from all of England in a service whose theme, after all, was love. Again, they rose and applauded, not just to the man and his tribute but to the fact that he was there at all - another victory over the purse-lipped Establishment.
There was an Irish reference too, a verse of the lonely Derry Air - I would be true, for there are those that trust me - sung without accompaniment by the boy choristers.
And as the heart-wrenching line from Tavener's Hamlet - May flights of angels sing thee to thy rest - rose pleading to the heavens, and the cortege slowly left the church, the agony seemed too much to bear. They stood, stunned, watching the flower-strewn hearse move slowly through the sun-dappled streets on their "golden child's" journey back to her island grave.
Many were still there, heads still bowed, as applause echoed across the lawns from the roadside, signifying her last passage down Park Lane.
What did it all mean, this outpouring of grief for a woman whom few of them had ever shared a town with, never mind a room, still less a friendship; a woman who met a shabby finale in a Paris tunnel and who was no sainted virgin? Was it all mere sentimentality or had Britain really undergone some fundamental catharsis?
"I have no idea," said a tear-stained Glenda Jenkins, "none at all. I don't even know why I came. The fact is, I'm a bit embarrassed about it. All I can say is that it was like the impulse I get to go to my mother's grave. I don't understand why, but it was the same kind of impulse that made me want to be here."
Her friend looked equally at a loss. Blowing her nose, she ventured: "Guilt maybe. I sneered a bit when she was alive. Now I don't know why I did that."
Then she thought a bit more and brightened: "You know, I feel so peaceful now, incredibly drained but incredibly peaceful. Maybe what we all needed was one really good cry, a huge emotional release. If that's catharsis, then I'm for it."
Back in Knightsbridge, Diana's home playground, lilies died beside her portrait in a 100 black-draped windows. Valentino, Armani, Prada, Cartier, Stephane Kelian were among her favourites who had closed for the day, some of them displaying pictures of her wearing their goods. "You will be greatly missed," said some of the signs. And her credit cards too.
Outside Harrods, also closed for the day, the queues continued unabated to sign the condolence for Di and Dodi. At Harvey Nichols, a smart-looking queue waited impatiently for the doors to open at 2 p.m. It was, after all, lunchtime.