ROBERT JOBSON: William and Harry may now understand their mother better. But not enough to keep their promise to her…

Diana, Princess of Wales, gave her boys a special assignment: “You must promise me that you will always be each other’s best friends,” she told them.

At the time, the brotherly promise seemed simple.

Their agreement was sealed with high-fives and a motherly hug. It speaks volumes about the late princess’s aspirations for William and Harry.

Sadly, this vow, revealed in royal historian Robert Lacey’s bestseller, Battle of the Brothers, has not stood the tumultuous tests of time.

More than a quarter of a century after Diana died in a car crash in Paris, her “boys” are now men and can barely speak to each other.

After what has happened in recent years, there seems little prospect of the bitter feud between them healing anytime soon.

A new statue at Kensington Palace, a silent testament to their mother’s legacy, briefly brought them together in July 2021, a lull in their estranged relationships, on the eve of what would have been Diana’s 60th birthday.

But it was a fleeting truce in a story marked by distance and disagreement.

Now tonight at The Diana Award – a worthy charity that captures the essence of their mother’s vision and belief in the transformative power of youth – the brothers will make a rare joint appearance to honor her at the Science Museum in London.

However, neither will be in the room at the same time – clearly a prerequisite – even virtually.

William will personally give a speech to mark the charity’s 25th anniversary and present awards to 20 recipients.

According to reports, Harry will take part in a video call with the winners, but only after his big brother has left.

In the past, they often appeared together in person to pose with the award winners.

What would she have made of it all?

“She would have butted heads, she wouldn’t have put up with it,” said one former loyal employee.

Diana’s upbringing, based on love and hugs, was also one of discipline. She would occasionally slap her or cut her ear when she felt the situation warranted it. She gave the babysitter permission to do the same.

It shaped William and Harry with a mix of royal duty and human frailty.

There was a lot of laughter and a few tears, the insider said. She made the boys do everyday chores, showing how she then wanted to grow up with a sense of normalcy, despite their royal rank.

She clashed with the staff who reminded them they were special.

Growing up, William and Harry were inseparable. They relied on each other in the aftermath of their parents’ estrangement and divorce.

Despite the normal rivalry between siblings, they always had each other’s backs throughout their school years, with Harry following William to Ludgrove and then to Eton.

Harry looked up to his brother, William always looked after Harry.

Their brotherly relationship, against the backdrop of loss, love and legacy, was always strong.

Who can forget the images of them at her funeral as they struggled with the colossal loss of their iconic mother.

Hearts around the world went out to the grieving sons she helped shape.

Robert Lacey also revealed in his book that Diana’s friend, Simone Simmons, recalled the princess also telling her boys, “Never let anyone come between you.”

“Both boys then promised that they would keep that promise and then went on to play football,” Lacey said.

It was typical Diana. Straight away. She was good with them, straightforward and firm when necessary.

Critics of her approach missed the point. They said she smothered them with love. But Diana made princes.

William and Harry, now parents themselves, may understand their mother better. But not enough…

Reconciliation seems a distant hope.

The gap between them reflects the complexity of their lives and the emotional burden they carry.

It’s sad but perhaps not surprising that they parted ways. The weight of history and personal grief under the watch of millions has marked the journey of two princes who seem to be searching for the promise they made to their mother long ago.