Our Mother Diana: Her Life and Legacy, which they made with ITV and HBO to commemorate the 20th anniversary of Diana's death.
As People reports, Harry opened up in the documentary about his final phone call with his mom, and the painful regret he still carries.Diana called William and Harry, then aged 15 and 12, hours before her fatal car crash.
The princes were staying at Balmoral, the Queen's Scottish estate, at the time. The final phone call was short, as the brothers were in the midst of a game with their cousins.
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