In an emotional interview, the princes revealed they were at the Queen’s Scottish retreat in Balmoral when they had their last phone call with their mother. Keen to return to playing with their cousins, they did not spend long on the phone with Diana when she called from Paris.
"I can't necessarily remember what I said but all I do remember is regretting the rest of my life how short the phone call was," Prince Harry said. “And if I’d known that that was the last time I was going to speak to my mother the things that I would – the things I would have said to her.
"Looking back at it now — it's incredibly hard. I have to deal with that for the rest of my life: not knowing that it was the last time I'd speak to my mum, how differently that conversation would have panned out if I'd had even the slightest inkling that her life was going to be taken that night."
"Harry and I were in a desperate rush to say 'goodbye, see you later, can I go off?'" Prince William said. "If I'd known what was going to happen I wouldn't have been so blasé about it. That phone call sticks in my mind quite heavily."
William went on to speak about how Diana would have been the "naughtiest" grandmother.
"We've got more photos up 'round the house now of her and we talk about her a bit and stuff," he explained. "It's hard because obviously Catherine didn't know her, so she cannot really provide that … level of detail. So, I do regularly, [when] putting George or Charlotte to bed, talk about her and just try to remind them that there are two grandmothers — there were two grandmothers — in their lives. It's important that they know who she was and that she existed."
"She'd be a nightmare grandmother, absolute nightmare," he joked. "She'd love the children to bits, but she'd be an absolute nightmare. She'd come and go and she'd come in probably at bath time, cause an amazing … scene, bubbles everywhere, bathwater all over the place, and then leave."
Harry also revealed he has only cried tears of grief twice, at her graveside at Althorp on September 6, 1997, and since then “maybe, maybe once. ”
“So there’s, you know, there’s a lot of — there’s a lot of grief that still needs to be let out," he said.“There’s not a day that William and I don’t wish that she was still around, and we wonder what kind of a mother she would be now, and what kind of a public role she would have, and what a difference she would be making.”
Diana, Our Mother: Her Life and Legacy airs this Sunday Night at 7.00 on Channel 7.