"It has been 20 years since our mother's death and the time is right to recognise her positive impact in the UK and around the world with a permanent statue," William, now 38, and Harry, now 36, said in a joint statement at the time.
"Our mother touched so many lives. We hope the statue will help all those who visit Kensington Palace to reflect on her life and her legacy."
When is it being unveiled?
The statue is set to be unveiled at 1pm, UK time, july 1, (1am New Zealand time, July 2), which would have been Diana's 60th birthday.
Royal watchers and fans are expecting to see the brothers come together after a fraught couple of years of feuding in the public eye.
The statue was initially meant to be unveiled in the tail end of 2017, however plans changed and in August 2020 the new date was named.
Where is it being installed?
In Diana's favourite spot, the Sunken Garden in the grounds of Kensington Palace.
"The statue will be installed in the Sunken Garden of Kensington Palace on 1st July 2021, marking The Princess's 60th birthday," the Dukes of Cambridge and Sussex announced at the time.
"The Princes hope that the statue will help all those who visit Kensington Palace to reflect on their mother's life and her legacy."
It's not the first tribute to me made to the People's Princess within these grounds. In 2017, on the 20th anniversary of her death, Diana's favourite flowers (which include forget-me-knots, white lilies, roses, tulips, daises and narcissi), were planted around the garden.
The white colour scheme was a nod to her personal style.
Who is sculpting the statue?
Somebody incredibly famous – sculptor Ian Rank-Broadley. Ian has had one very important project for the royals before this statue.
He was the artist behind the designed image of the Queen that is used on the UK's coins.
A fitting artist for the job.
Who is attending the unveiling?
The two brothers are a sure thing, with Harry, who lives in the US with his wife, the Duchess of Sussex, Meghan Markle, and their two children, arrived in the UK last week in order to complete his quarantine ahead of Thursday's event.
While we are unsure who exactly will be attending the event, this week it was learned that Prince Charles and the Duchess of Cambridge, Kate Middleton, would not be attending.
According to reports, Prince Charles won't be at the unveiling of a statue of his late former wife Princess Diana because the event could dredge up the painful past.
An insider told the UK Times that: "He does find it terribly difficult. These moments have the potential to resurface old wounds, and it brings back memories for him; happy, sad, regretful. Since Diana's death, he has felt it's best to keep those memories to himself and leave his sons to it."
Charles and Diana separated in 1992 and divorced in 1996, a year before her death in a Paris car crash.
As for Kate, her absence from Princess Diana's memorial launch Thursday will be "telling on so many levels", say family sources.
Prince William's wife is missing out on the unveiling of a statue after the guest list was slashed.
And while it had been expected Kate would be on hand to broker peace between William and his brother Prince Harry, a source told Page Six: "Catherine's absence speaks volumes.
"I think keeping the numbers down is a perfect 'excuse' for Catherine to stay away. William is fed up with the drama and Catherine doesn't need to be dragged into this.
"They are planning a private family visit with their children, and that private moment is far more important than the public rhetoric."
This news came after it was revealed that the event had been drastically scaled back in recent days from the 100-plus guests originally planned due to Covid-19-related rules.
Unsurprisingly, Meghan Markle will not be in attendance either, opting to stay at home in Montecito, California, with her newborn daughter Lilibet, and 2-year-old son Archie.
Kensington Palace has also confirmed that close members of Diana's family will be in attendance.
Will Prince William and Prince Harry show a united front?
The brothers are likely to ensure that the attention of the day is about their mother, and not on their strained relationship.
In doing so, the brothers have insisted on doing separate speeches, reveals a source who spoke to The Sun.
"The brothers will be physically together for the ceremony but want to make their own personal addresses. You might have thought they'd go for a joint statement and speech but that's not the case. Each has insisted on preparing their own. It is a big concern that their body language will suggest all is not well and they won't present a united front."
While things have been incredibly tense between William and Harry since the latter stepped away from his senior royal duties with wife Meghan, it is said they have kept the dealings with the statue drama free.
A source told The Sun: "It will have been signed off by William and Harry, that much I do know. I know [sculptor Ian Rank-Broadley] did work closely with the boys and I think it will be incredible."
The publication also reports that William and Harry's cousin Zara Tindall and her husband, Mike Tindall, have been "playing peacemakers" between the brothers over the past year.
Despite all of this, it is no secret that the brothers are not in a good place at the moment.