During an emotional speech at the Sentebale Polo Club in Aspen, Colorado, the Duke of Sussex told his captive audience how he will  commemorate the 25th anniversary of his late mother, Princess Diana, this week.

Prince Harry, 37, who flew in a private jet on August 25 to compete in a polo tournament to raise money for Sentebale’s work with young people from Lesotho and Botswana in southern Africa, said he would be with his wife Meghan Markle and children, Archie, aged three, and Lilibet, aged one.

He will not be with his older brother Prince William in Britain, as both have reportedly agreed not to commemorate Diana’s 1997 death in public again.

William, his wife Kate Middleton and their children, George, Charlotte and Louis, will be settling into their new residence at Adelaide Cottage in Windsor. Harry and Meghan will be at their Montecito, California, estate.

“[August 31] is the 25th anniversary of my mother’s death and she most certainly will never be forgotten,” Harry told the crowd at the Aspen reception.

“I want it to be a day filled with memories of her incredible work and love for the way that she did it.

“I want it to be a day to share the spirit of my mum with my family, with my children who I wish could have met her. Every day I hope to do her proud,” he said, with no mention of William.

“Fittingly, her favourite flowers were forget-me-nots.

“She was tireless in her work to support and de-stigmatise those experiencing HIV and AIDS. I hope we can remember my mother’s legacy by recommitting to those that we serve, whoever and wherever they may be.”

Harry established Sentebale, which means “forget-me-not” in Sesotho, to honour Diana. The charity was founded in Lesotho in 2006 by Harry and his friend and mentor, Prince Seeiso.

‘‘For Sentebale, our commitment is to ending HIV and providing meaningful care and support for the children and young people whose lives have been affected by this disease. Because they too will never be forgotten,’’ he said.

Tweet from @SussexEvent

Brothers, once united in grief

Just after midnight on August 31, 1997, Diana was involved in a car crash in the Pont de l’Alma tunnel in Paris, along with her boyfriend Dodi al-Fayed and chauffeur Henri Paul, the driver of the Mercedes-Benz W140 S-Class in which she was travelling.

She died in a Paris hospital hours later.

Harry was just 12 years old and William was 15.

According to London’s Telegraph newspaper, the brothers have ‘‘agreed to draw a line under their public commemorations’’.

‘‘The brothers will each remember Diana, Princess of Wales, with their own wives and children, none of whom were able to meet her,’’ the newspaper reported.

The brothers were united in a public display of grief in 2017 for the 20th anniversary of Diana’s death and undertook major commemorations in her name. They included the creation of a memorial garden at Kensington Palace.

They revisited the palace’s gold gate where, two decades earlier, there was a huge floral memorial from a grief-stricken nation.

It was a smaller memorial and their visit was an impromptu moment, as they were there officially to visit Diana’s White Garden, but once they saw the tribute, they went to pay their respects and well-wishers handed the princes bouquets to lay down.

Tweet from @KensingtonRoyal

“The Duke and Prince Harry are grateful for the many flowers, letters, and messages they have received about their mother,” Kensington Palace tweeted.

“They wanted to say thank you to those who made the journey to Kensington Palace.”

Fast forward to now.

‘‘The Telegraph understands both dukes have made it clear that the 20th anniversary would be the last milestone anniversary they would mark in public for the foreseeable future.

‘‘Having shared their memories of their mother and paid tribute to her legacy in person and on television, they will now continue to grieve privately on the anniversary each year.

‘‘A source said the day was still a painful one for the late Princess’s sons.

‘‘Friends of each brother separately emphasised that they would still mark it in their own ways, talking about ‘granny’ with their young children.’’

A spokesman for Kensington Palace and a spokeswoman for the Sussexes separately confirmed that this year’s anniversary on Wednesday would be spent privately, reported The Telegraph.

In happier days, maybe. Harry, Meghan, Kate and William in their first joint gig. Photo: Getty

Brothers divided since Harry’s 2020 move to the US

Although there were reported royal misgivings about Harry marrying Meghan long before their 2018 wedding, the Duke and Duchess of Sussex’s two years of married life in Britain were marred with rumblings of discontent between the brothers.

First there were the newspaper headlines about Meghan reportedly bullying her staff, negotiations over Harry’s future role and the legal constraints on using Sussex Royal as a promotional tool.

Then there was the tabloid media and how it reported Meghan’s difficult relationship with her father, and how William and Charles urged Harry to sort it out.

Over Christmas in 2017, Vanity Fair’s royal reporter Katie Nicholl said Harry told William he wasn’t doing enough to include Meghan, and needed to ‘‘roll out the red carpet’’ for her.

In his 2019 documentary, Harry and Meghan: An African Journey, Harry confessed that he and the future king were ‘‘on different paths’’.

‘‘Look, we’re brothers. We’ll always be brothers. We’re certainly on different paths at the moment, but I’ll always be there for him as I know he’ll always be there for me.’’

That same year, the announcement that the royal foundation would no longer be a philanthropic vehicle for both couples, just the Cambridges, was one of many fractures.

By 2020, after the Sussex’s six-week stint in Vancouver over summer, and a quick awkward reunion for the funeral of the princes’ grandfather Prince Philip, there was no turning back.

Enter Oprah Winfrey … and the dreaded docos and podcasts … and the brothers’ relationship was finally determined.

In March last year, after Harry and Meghan had officially moved to the US, they sat down with the talk show queen, where they unleashed on the royal family, calling them racists.

In May, Harry’s mental health documentary series You Can’t See Me created more tension, with him saying being part of the royal family was like living in a zoo.

In June, the Sussexes joined the royal family at a thanksgiving service in London as part of the Queen’s platinum jubilee celebrations. It was their first public appearance in Britain since they quit royal duties.

Harry and Meghan are concentrating on forging a new life in California with multimillion-dollar Spotify and Netflix deals (not to mention his forthcoming memoir).

Tweet from @TheLeague_LA

So, where to from here?

William and Harry will most likely issue separate statements on their social media platforms on August 31, but it is not clear what William’s official program as second in line to the throne will be.

On the 23rd anniversary of Diana’s death, Harry planted forget-me-nots at a pre-school in Los Angeles in post-royal life.

He may do something similar before he and Meghan, hot off the success of her Archetypes podcast reaching No.1 on Spotify in Britain and the US, attend a summit for young leaders in Manchester on September 5, and an awards ceremony for seriously ill children on September 8.

They will also attend an event in Germany on September 6 to mark one year before the 2023 Invictus Games for injured veterans. The games will be held in Dusseldorf.