Princess Diana Longed to Reunite with Prince William and Prince Harry on Final Call Before Her Death

Anwar Hussein/WireImage Princess Diana

One of Princess Diana's close confidants is revisiting their final phone call on the night of her shocking 1997 death in Paris.

Richard Kay, a longtime royal reporter and friend of the princess, looks back on the telephone conversation that would turn out to be the Princess of Wales' last for the upcoming Diana documentary, airing Thursday night in the U.K.

"I spoke to her that night," he recalls - though only later, once the 36-year-old had died in a car crash resulting from a high-speed paparazzi chase, would Kay realize how significant that call was. "[The] police said that the last call she made was to me."

The mother of Prince William and Prince Harry, then 15 and 12, was "in quite a good place," shares Kay, according to The Mirror. But above all, "she wanted to come back and see her boys."

Diana was also eager to turn a new page in her life. "She was desperate to try and make a fresh start and do something different," says Kay, "to explore a different kind of royalty."

What Diana would tragically never come to realize, in fact, was that even in death she would reshape the monarchy, setting off ripples through her legacy, her love for her children and her compassion.

Get the latest issue of PEOPLE Royals for inside stories royals fans haven't seen or read elsewhere! Subscribe at peopleroyals.com/launch

Kay is just one the of many friends and family members who are coming forward to remember "The People's Princess" in the weeks ahead of July 1, which would have been her 60th birthday.

Her sons will also be coming together - reuniting for the first time since the funeral of their grandfather Prince Philip in May - to commemorate their mother on her birthday by unveiling a statue dedicated to her on the grounds of Kensington Palace.

"It will be an emotional day," said her brother Charles, Earl of Spencer, "but it will be a tribute to a much missed and much loved sister, mother, etc."

Julian Parker/UK Press via Getty Princess Diana, Prince Harry and Prince William

Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!

Indeed, tributes to Diana have been flowing recently, from a subtle nod William's wife, Kate Middleton, Duchess of Cambridge made through her jewelry on June 11 to the middle name of Harry and wife Meghan Markle's first daughter, who was born on June 4.

Baby Lili shares her middle name with her 6-year-old cousin, William and Kate's daughter Princess Charlotte. And Diana's friend and personal astrologer said that homage by her two sons would have moved her deeply.

"Diana would have been so touched by both her granddaughters sharing her name," Debbie Frank recently told PEOPLE. "She would have been absolutely thrilled, and it's a beautiful gesture of love from both her boys."