The estranged prince attended his father's coronation, but stayed in the background during much of the ceremony.
The royal couple was joined by Prince William and Kate Middleton, as well as their children, Prince George -- who had an important and historic role in the coronation -- Princess Charlotte and Prince Louis.
Other working royals who joined the family on the balcony included Charles' siblings, Anne, Princess Royal, and Prince Edward, Duke of Edinburgh, as well as their children. Embattled fourth sibling Prince Andrew was kept in the background during the coronation proceedings and did not join his siblings as they waved to the gathered crowds.
However, one family member was notably missing from the royal photo op: Charles' younger son, Prince Harry, who attended the coronation for his estranged father, but sat with his cousins and did not serve an official role in the ceremony.
During the coronation, Harry sat alongside Princess Beatrice and Princes Eugenie, and their respective spouses. He seemed in good spirits, smiling and chatting, and also joined attendees in reciting "God save King Charles" following his father's crowning and sang along to "God Save the King" as the monarchs processed out of Westminster Abbey.
Following the ceremony, Harry was seen getting into a black BMW sedan, and departing Westminster Abbey.
ET spoke with royal expert Eloise Parker ahead of the May 6 ceremony, who shared some insights on what would likely go down between Harry and Charles during the coronation and it wasn't too far off from what viewers saw Saturday.
"I fully expect Prince Harry to be very much on the sidelines during this ceremony," Parker shared. "This ceremony is all about King Charles III and the Queen Consort, so I would expect even the Prince and Princess of Wales, William and Kate, will also be at the sidelines for this [event]."
It was recently revealed that Harry would be attending the coronation alone -- while his wife, Meghan Markle, and their two children -- Archie, who turns 4 on Saturday, and Lilibet, 1 -- will remain at home in California.
"[There was] some surprise that Harry is going alone, [but] not so much when you realize that it's his son, Archie's, birthday the very same day," Parker explained. "So Meghan is in fact going to be staying home in California to celebrate that birthday, which is perhaps quite convenient given the tensions between the two families right now."
A source told ET that Harry arrived in the U.K. on Friday morning, and was put up at his and Meghan's former home, Frogmore Cottage. He is expected to depart on Saturday following the coronation festivities. Meanwhile, ET has learned that Archie’s birthday celebration will be a small gathering with friends and family in Montecito.
While Harry attended solo -- and stayed out of the spotlight, for the most part --- Parker said it is "impossible to believe there's not gonna be some amount of tension, given just how intimate Harry's revelations were for the entire family in his book, Spare."
"I think this is the first time they're gonna be in person since the launch of that book," Parker added, noting that most of the attention will be on Charles on Saturday.
"There's going to be thousands of people around, all needing attention, Charles is gonna be very much at the center of that, so hopefully for Harry that's gonna take the emphasis off him," Parker shared. "I think most people are hoping that the father-son relationship will heal over time. Unfortunately, I just don't think the coronation is gonna be the event for that to happen."
"There's just gonna be too many people, too much pressure, and far too much going on," she said, adding that any eventual reconciliation is almost certainly going to come after the highly public royal event.
Although the actual anointment during the coronation ceremony was not broadcast publicly, plenty of special programming and footage from the ceremony is available to watch on CBS and Paramount+. Audiences will also be able to view coverage on CBS News, including the concert featuring Katy Perry and Lionel Richie on Sunday, May 7. Additionally, others can watch the coronation online on these streaming platforms.