King Charles Hugs Zara Tindall at Horse Show Closely Tied to Queen Elizabeth amid Cancer Treatment

King Charles is returning to a classic event on the royal family's calendar.

On Friday, May 3, the King, 75, attended the annual Royal Windsor Horse Show, held in Home Park at Windsor Castle.

During the event, Charles was pictured greeting his niece Zara Tindall with a warm hug and a smile as the pair wrapped their arms around one another.

The King kept warm in a beige trench coat, while the 42-year-old daughter of his sister Princess Anne sported a dark gray checkered jacket.

The monarch's appearance at the equestrian event, which runs from May 1 to May 5, was significant for several reasons. Not only did it mark Charles' first informal day out after resuming forward-facing royal duties while receiving treatment for cancer, but also his first appearance at the Royal Windsor Horse Show for 45 years! 

The horse show was a staple on the late Queen Elizabeth’s calendar throughout her record reign, and she last attended in 2022 after missing the State Opening of Parliament earlier in the week amid mobility issues. Queen Elizabeth was all smiles as she caught the competition ringside with her son Prince Edward, daughter-in-law Sophie, the Duchess of Edinburgh and royal family friend Penny Knatchbull.

The group was in for a treat when the Queen's horse, Balmoral Leia, won the Highland class.

"She was in great spirits," an observer told PEOPLE about Queen Elizabeth's presence at the event that day. "You can see she is in really good form."

Her eldest son, meanwhile, was last photographed at the multi-discipline competition in 1979, when he competed in a triathlon event on his horse Candlewick.

On April 30, King Charles stepped out for his first official pubic-facing engagement since Buckingham Palace announced the news about his health in February. He visited the Macmillan Cancer Centre at the University College Hospital London with Queen Camilla, making the stop to  emphasize the importance of early detection and learn more about the research happening at the hospital. 

The royal couple spent much of the visit meeting patients and staff. It's understood that the center has not been directly involved with the King’s medical care.

"I think he was really thrilled to be out," Queen Camilla, 76, said at a Buckingham Palace reception she hosted the following day, according to the Daily Mail.

"I've been trying to hold him back," the Queen added about how her husband has been feeling in recent months.

Buckingham Palace announced the King’s visit to the cancer center a few days before the significant stop, outlining that it was the first of several engagements planned for him in the coming weeks, including a state visit with the Emperor and Empress of Japan in late June.

After starting cancer treatment in February, King Charles postponed public duties but continued to work behind the scenes and undertake meetings, such as small audiences at Buckingham Palace. However, a royal source previously told PEOPLE that the monarch's desire to work was "wholly undiminished," with his nephew Peter Phillips mentioning in an interview that his uncle was in "good spirits" but "frustrated" by his limitations.

In the April 26 announcement about the King’s return to public-facing work, Buckingham Palace said that his treatment was ongoing and shared a positive sentiment from his doctors.

"His Majesty’s treatment program will continue, but doctors are sufficiently pleased with the progress made so far that The King is now able to resume a number of public-facing duties. Forthcoming engagements will be adapted where necessary to minimize any risks to His Majesty’s continued recovery," a spokesperson said.

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Looking ahead, his attendance has not yet been confirmed for upcoming summer events on the royal calendar like Trooping the Colour, Royal Ascot or Buckingham Palace garden parties.

"Planning continues for ways in which Their Majesties may attend such summer and autumn engagements, though nothing can be confirmed or guaranteed at this stage. All future plans remain subject to doctors’ advice nearer the time, with appropriate adaptations made where necessary to minimize any risks to His Majesty’s continued recovery," a palace spokesperson said.