All eyes were on the Duke of Sussex as he arrived at the ceremony earlier this morning, without his wife Meghan Markle, who has remained at home in California with the couple's children, Prince Archie, four, and Princess Lilibet, one.
However, if fans were expecting Harry to be nervous or anxious about appearing solo at the historical event, they may have been surprised as the duke instead put on a defiant display, according to body language expert, Judi James.
"Prince Harry’s appearance at Westminster Abbey was a total, counter-intuitive shock from the rebel Prince who was now going to be placed three rows back on the ‘naughty step’," James, who was speaking to Paddy Power Bingo, explains.
Harry arrived at the event alongside his cousins Princess Beatrice and Princess Eugenie and their respective partners and James believes the duke appeared to be in good spirits.
"Harry’s entrance with his wing-men cousins of the ever-loyal Beatrice, Eugenie and their husbands, looked like a return of the joker Prince, as though the rifts and anguish of the past few years had never happened," she says.
"Smiling with a very authentic-looking, rounded-cheek smile or grin, Harry was seen joking and laughing with his cousins, even miming Eugenie’s heavily-pregnant bump to make her and husband Jack laugh."
While Harry walked into the ceremony on his own, James says there was an air of confidence around the royal.
"Harry chose to walk in alone, however, his body language produced the opposite, making it look like the return of the prodigal son rather than any walk of shame," she explains.
"He chatted to the clergy before setting off down the aisle with a slightly rolling, wide-stride gait that looked cocky and confident.
"Unlike other guests, who had tended to walk quickly while looking nervously ahead, Harry used eyebrow-flashes as small tie-signs of connection with the congregation, also grinning and even chatting as he spotted several old friends."
Royal fans were no doubt watching out for any interaction between Harry and his brother William and his wife Kate, but James says the duke appeared to look away when the couple made their own entrance.
"Harry had been in an in-depth discussion with Edoardo that included giggling laughter with Harry placing his tongue-tip between his teeth before both men did a mirrored closed-lip smile that looked like mutual sympathy," she explains.
As the King arrived, James says Harry became "watchful", but this seemed to change as his father walked past with his brother and the Princess of Wales.
"As Charles, William and Kate walked by, Harry turned his head to talk to Edoardo again in what looked like an act of rejection or deliberate ignore," she explains.
"All eyes were on the royal party apart from Harry’s, and I would imagine he was the only person there wanting to indulge in a little chat at that moment."
James also gave her insights on the King's body language signals during the prestigious event, explaining that as he progressed up the aisle Charles looked "tense and rather bashful" possibly indicating some nerves.
"His facial expression did soften and relax a little as he saw friendly faces he recognised but he clearly braced himself first by sucking in his lower lip and tapping his fingers together, with a gentle and constant rubbing of his fingers over the golden knot in his regalia continuing the entire walk."
While James said his mother, the late Queen Elizabeth II, retained an air of steely composure during her own coronation, she believes Charles looked surprisingly vulnerable with many of his signals suggesting "a desire to lower his status slightly rather than raise it regally".
"He looked like a man unwilling to be elevated away from the public and away from the people he loves to surround himself with," she explains. "Hunched in his carriage, his waves were brief ‘waggling hand’ waves, rather than the more rigid royal wave."
The King's body language, she says, leaked signals of "defined anxiety".
"From the self-comfort thumb rubbing to the way he constantly played with and rubbed the knot in his golden belt," James explains. "At times he looked in danger of being overwhelmed by emotion and even when he walked out to greet the cheering crowds there was no apparent sign of relaxation."
James believes these traits will probably serve him well in terms of his popularity as King, however.
"Pomp and high status don’t sit well with a modern nation and Charles’ vulnerability and underlying anxiety will make him more accessible and even loveable."
The moments when his face softened into a warm smile of gratitude or affection, like his fleeting smile at William during the ceremony, James says, show the strength of his honest emotions.
"And the small, knowing grimace when he managed to get the lid back onto his fountain pen after nightmare battles with pens on two previous occasions suggested that, despite the formality and sense of history, he wasn’t taking himself too seriously."
His wife, Queen Camilla, on the other hand, displayed anxiety levels lower than usual, says James.
"This suggests she was desperate to offer signals of support and strength to her husband," she says.
"It was only once the crown was on her head that she produced a really wide smile and began to communicate with nods, smiles and glances to the rest of the congregation."
Kate and William’s children were almost a masterclass in good behaviour, especially Louis, who is around the same age as Charles was when he attended the late Queen’s Coronation.
"Louis really did show his grandad how it should be done," James says. "Going back 70 years, the young Charles was seen looking bored and tetchy, prompting the Queen Mother to pull him back from leaning over the balcony, whereas Louis stood upright and straight-faced, singing the anthem from memory and with enthusiasm, and only doing a couple of yawns to suggest he was anything but enthralled.
"George clicked to attention as he stood with Charles’ train and Charlotte created the perfect double act with her mother, wearing a matching tiara as the two exchanged glances and smiles."