The call that changed the monarchy forever came shortly after 1am at Balmoral Castle.
The Queen, her husband Philip and their heir, Prince Charles, were roused from their beds and informed of the news.
Princess Diana — once seen as the saviour of the House of Windsor before she was exiled — had been in a car crash in Paris.
Initially it was believed that she had walked away with a broken arm, leading the Queen to crack a joke that would haunt her and fuel conspiracy theories for decades to come.
"Someone must have greased the brakes," she said.
As night edged towards dawn, the family realised that something was terribly wrong.
A palace aide broke the news to Charles at 4am.
"Sir, I am very sorry to have to tell you that I've just had the ambassador on the phone. The Princess died a short time ago," he was told.
Diana's former husband began to weep, repeating to no-one in particular: "What have we done to deserve this?"
But the then-71-year-old Queen, who had steered her kingdom through war, terrorist attacks and familial drama for four decades, immediately sprung into action.
She ordered the radios and televisions to be removed from the nursery where Diana's sons were still asleep and totally unaware of the tragedy unfolding around them.
Next, she dispatched Charles to Paris to identify the mother of his children.
And she asked her aides to check in with Diana's family, the Spencers, about funeral arrangements.
But what Queen Elizabeth II did not realise was that she was about to enter the most dangerous and tumultuous week of her reign.
While her aides went to war with Charles, the House of Spencer and newly installed prime minister Tony Blair, the Queen's subjects unleashed a howl of agonised grief unlike anything she had ever seen.
An outpouring of grief unlike any other
At 5am, the BBC broke the news of Diana's death to the public.
By 5:30am, floods of mourners were weeping and praying at the gates of Buckingham and Kensington palaces, leaving tributes of flowers, candles and teddy bears.
Within days, there were said to be a million bouquets piled up outside Diana's home at Kensington Palace, stretching metres out from the gates.
Diana might have been stripped of her HRH title and on the outer with the family when she died, but she remained Britain's most popular royal.
It was a visibly emotional Mr Blair who captured the mood of the public when, dressed in black and with his voice trembling, he declared Diana the "people's princess".
"They liked her. They loved her. They regarded her as one of the people," he said.
But public grief soon gave way to anger over the royal family's absence from London, their refusal to fly the Union flag at half-mast at Buckingham Palace and the Queen's lack of empathy for her subjects' mourning.
"You were a rose among a family of thorns," read one hostile message left outside Buckingham Palace.
The British tabloid press were just as scathing: "Has the House of Windsor a heart?" asked the Daily Mail. The Express demanded the royal family "Show us you care".
Reports of what was unfolding in London soon made their way to the family in Scotland, where the Queen and Prince Charles were preoccupied with the vulnerable William and Harry.
Queen Elizabeth II had been adamant that her place was at Balmoral with her grieving grandsons, according to Tina Brown, author of The Diana Chronicles.
She wanted to keep the young princes out of the public spotlight and surrounded by loved ones.
Prince William would later recall how the time away had allowed the brothers to, "collect our thoughts and have that space away from everybody".
The Queen's first instinct, to remain secluded at Balmoral may well have been the right one, says historian, author and royal commentator Carolyn Harris.
As anger built on the streets of London, comparisons were drawn between the palace's indifference to Diana in her death and its treatment of her as a princess.
"There was a lot of public pressure to return to London and for this to be a big public funeral," Harris said.
Just days out from laying Diana to rest, the family's stony resolve was finally shaken.
The Palace decided to send princes Andrew and Edward to meet the grieving public to test the mood, before issuing a rare public statement.
Queen Elizabeth II also relented on the issue of the flag, allowing the Union Jack to fly at half-mast at Buckingham Palace for the first time.
As the royals prepared to take on the media, another war was brewing inside the House of Windsor.
An icy narrative sets in as in-fighting takes over
Initially, much of the public and private outrage over Diana's death was directed towards the paparazzi, who had been chasing the young princess and Dodi Al Fayed's car into the Pont de l'Alma tunnel when they crashed.
Only a week before her death, Diana had described the insatiable media pack that followed her throughout her life as "ferocious" in the French newspaper Le Monde.
Upon hearing the news of her death, her brother Earl Spencer declared: "I always believed the press would kill her in the end."
He told reporters that every editor who had ever paid for "intrusive and exploitative photographs" of the Princess had "blood on their hands".
The British public seemed to be of a similar opinion. Four days after the fatal crash, a Gallup poll found more than 70 per cent of those surveyed in Britain held the photographers responsible, with 43 per cent opting for "extremely".
But it didn't take long for this wave of anger to shift towards the Windsors and their failure to protect Diana from the relentless hounding of the press.
Andrew Morton, a royal reporter who wrote a blistering tell-all about Diana in 1992, based on secretly recorded tapes she smuggled out of Kensington Palace, said Charles was keenly aware that he was an obvious target for blame.
"The Prince's spin doctors at St James's Palace tried to portray Charles as decisive and democratic, while painting all the Queen's men as dithering, delaying and hiding behind precedent and tradition," he wrote in his book, The Queen.
At one point, a story was fed to the British tabloids suggesting it was the Queen herself who refused to send her plane to retrieve Diana's casket from France.
But in reality, according to Morton, the Queen had never hesitated in her decision to claim Diana's body and the story was false.
"In short, Charles's camp were prepared to throw anyone under the bus in order to protect their man — and that included the Queen," Morton wrote.
As tensions mounted between Charles and the Queen, there was also discord between the monarch and the prime minister.
Mr Blair's coining of the phrase "people's princess"— according to some observers — was not entirely welcomed by the Queen, Morton wrote.
"Indeed, it initially led to a degree of strain," he added.
With the royal family seemingly divided and at odds with England's leader, the monarch's personal approval rating dipped, according to IPSOS polls, to 66 per cent.
Prince Charles's rating dropped to 42 per cent, with only 36 per cent believing he should ever be crowned king.
The royals had survived scandals, divorces and tell-alls but, in a matter of days, the death of the people's princess and the House of Windsor's response had almost toppled the monarchy.
The future of the institution rested on the family's next steps.
The Queen breaks all her own rules and addresses the kingdom
On September 5, the fever of public anger was broken in an instant by the Queen's arrival in London.
Only five days had passed since Diana's death, but the monarchy was in turmoil.
The Prince of Wales, the prime minister and numerous royal advisers were worried that the Queen's actions were threatening the institution, according to Morton.
Queen Elizabeth II — at the urging of those around her — cut short the family's stay at Balmoral and returned to the palace a day early.
"At Balmoral, she hadn't taken it in. You never know what it is like until you are actually there," a senior aide explained to Morton.
As Prince Charles and his sons made an unannounced visit to see the floral tributes left outside Kensington Palace, the Queen and Prince Philip set to work on a special televised address from Buckingham Palace — only the second of her reign.
At 6pm, the head of the Commonwealth spoke live to the nation, telling viewers that she would be speaking to them as both a Queen and a grandmother, "from the heart".
"No-one who knew Diana will ever forget her. Millions of others who never met her, but felt they knew her, will remember her," she said.
"I, for one, believe there are lessons to be drawn from her life and from the extraordinary and moving reaction to her death."
It was significant that the Queen wanted to present herself as both monarch and matriarch, according to Harris.
The speech won over the angry hordes at home. However, as the tension outside vanished, inside the palace, concerns turned to Diana's funeral.
Pointed barbs towards the royal family in the eulogy that her brother, Earl Spencer, delivered to tens of millions listening across the world did little to ease the rift.
"We, your blood family, will do all we can to continue the imaginative and loving way in which you were steering these two exceptional young men so that their souls are not simply immersed by duty and tradition, but can sing openly as you planned," Earl Spencer said.
The mention of blood family caught the attention of observers, emphasising the divide between Diana and Charles, and the people's princess from the sovereign.
Diana had won over the public with her warmth and charisma in what became a stark contrast to the Windsors' deliberate display of cold stoicism.
The British monarchy's commitment to "never explain, never complain" had buckled under the weight of public criticism.
It was not simply enough for the Windsors to be seen anymore, especially after Diana's disruption of the old model.
To earn the public's faith going forward, the Queen had to change the way she engaged with her subjects.
Ultimately, her Diana address became the first of a series of changes the monarch underwent to rehabilitate her image.
It may have only been one week in the Queen's long reign, but the lessons she took away from the people's princess would last a lifetime.
