Diana, Princess of Wales would have been best friends with Meghan Markle and jumping up and down in excitement at news of the royal engagement, Prince Harry has said.
The Prince paid a poignant tribute to his late mother, proposing to his American actress girlfriend Ms Markle with a ring made from diamonds from Diana's personal collection.
Harry said he made the gesture because he wanted the princess, who died in a car crash in 1997, to be part of his and Ms Markle's "crazy journey together".
He spoke of how much he missed his mother, saying: "It is days like today when I really miss having her around, and miss being able to share the happy news.
"But you know, with the ring and with everything else that's going on, I'm sure she's with us, you know, jumping up and down somewhere else."
Ms Markle echoed his thoughts saying: "She's with us."
The bride-to-be's engagement ring features two diamonds from Diana's personal collection, and a stone from one of their favourite places, Botswana.
Harry said: "The ring is, is obviously yellow gold because that's her favourite, and the main stone itself I sourced from Botswana, and the little diamonds either side are from my mother's jewellery collection, to make sure that she's with us on this crazy journey together."
Ms Markle added: "It's beautiful, and he designed it. It's incredible."
Harry joked: "Yeah, make sure it stays on that finger." Ms Markle replied: "Of course."
Ms Markle said: "Not being able to meet his mom, it's so important to me to know that she's a part of this with us."
She revealed she had met Diana's sisters and the princess's close friend Julia Samuel.
"I'm able to, in some way, know a part of her through them, and of course through him," she said.
"It's incredibly special to be able to have this," she said of the ring, adding: "It's perfect."
Asked what his mother would have thought of Ms Markle, Harry replied: "Oh they'd be thick as thieves, without question.
"I think she would be over the moon, jumping up and down, you know, so excited for me, but then, as I said, would have probably been best friends - best friends with Meghan."
The announcement of the couple's engagement after a whirlwind 16-month romance comes in the year that marked the 20th anniversary of Diana's death.
Harry and Ms Markle's photocall was held in the Sunken Garden of Kensington Palace - the site of the memorial garden created in the princess's memory to commemorate two decades since she was killed.
The Sunken Garden was one of the princess's favourite parts of the palace grounds.
When Harry's older brother William proposed to Kate Middleton, he used Diana's engagement ring.
"It was my way of making sure my mother didn't miss out on today and the excitement, and the fact that we're going to spend the rest of our lives together," William said in 2010.