London (CNN)When Prince Harry and Meghan Markle tie the knot in Windsor's St. George's Chapel, there's one person whose absence will be keenly felt: Diana, Princess of Wales.
Princess Diana: The small ways she'll be present at Harry and Meghan's wedding
But small details in the planning of the wedding make it clear that Harry wants his beloved mother's presence to be felt despite her early death in a road accident in Paris in 1997.
In a BBC interview last November marking his engagement to Markle, he spoke of his conviction that his fiancée and his mother would have been firm friends. "They'd be thick as thieves, without question," Harry said. "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 with Meghan."
Here are some of the ways in which Diana will be recalled at the wedding.
Harry included two diamonds from his mother's own jewelry collection in Meghan's engagement ring, which he designed himself, "to make sure she's with us on this crazy journey together," he said. They flank a central diamond from Botswana, where the couple's relationship blossomed.
"It is days like today when I really miss having her around and miss being able to share the happy news, but with the ring and with everything else that's going on I'm sure she's with us, jumping up and down somewhere else," Harry said in the November interview.
There has been speculation in the UK press that Markle may wear the Spencer family tiara -- worn by Diana for her own marriage to Prince Charles -- as "something borrowed" on her wedding day.
Harry's older brother, Prince William, gave their mother's famous diamond-and-sapphire engagement ring to Kate Middleton, now the Duchess of Cambridge, when he proposed to her in 2010. She will no doubt be wearing it for her brother-in-law's big day.
Harry and Meghan's chosen florist, Philippa Craddock, will be decking out the chapel with white garden roses, among other blooms. White roses were a favorite of Diana's and were included when one of the gardens at Kensington Palace -- where Harry and Meghan live in a cottage -- was transformed into a "White Garden" last year to mark the 20th anniversary of her death.
Crown Estate gardeners have been busy growing and preparing the flowers that will fill the church on Harry and Meghan's wedding day.
The couple have invited Diana's younger brother, Earl Charles Spencer, and her two older sisters, Lady Sarah McCorquodale and Lady Jane Fellowes, to the wedding. The latter has been chosen to give the reading at the ceremony.
"Prince Harry and Ms. Markle both feel honoured that Lady Jane will be representing her family and helping to celebrate the memory of the late Princess on the wedding day," said a palace statement.
Lord Spencer's heartfelt eulogy at his sister's funeral, in which he pledged that her "blood family" would do all they could to steer her sons' upbringing "so that their souls are not simply immersed by duty and tradition," reportedly caused a rift with the royal family that has taken years to heal.
Diana was laid to rest on an island in a lake on the Spencers' ancestral Althorp Estate.
Observers have noted qualities in Harry's bride-to-be that recall those of his mother. Like Diana, Markle is passionate about humanitarian and social causes -- and is outspoken in her support of them.
Although she has had to cut her past ties with organizations such as UN Women and World Vision as she takes on her royal role, Markle has made clear that she intends to continue her charitable work after the wedding.
On their first official joint royal appearance, less than a week after their engagement was announced, the couple visited a charity fair organized by the HIV/AIDS charity the Terrence Higgins Trust, marking World AIDS Day.
Markle has also already appeared at a Royal Foundation event alongside Harry, William and Catherine. The foundation brings together the young royals' charitable and campaign work, focused on helping young people, those with mental health issues, present and former servicemen and women and environmental conservation.
Diana devoted her efforts to charities helping homeless and disabled people, children and people with HIV/AIDS, and also campaigned against the use of landmines.
A photograph of her shaking the hand of a man with AIDS in 1987 did much to help to break down stigma around the illness -- and her passion inspired Harry to carry on her work.
That in turn helped him and Markle forge a bond from their first date. "Both of us have passions for wanting to make change, change for good," said Harry in their joint interview.
"It was really one of the first things we connected on," said Markle. "One of the first things we started talking about when we met was just the different things we wanted to do in the world and how passionate we were about seeing change. I think that was what got date two in the books probably."