A Heartbreaking Anniversary: King Charles and Queen Camilla to Mark Upcoming Milestone as Monarch Battles Cancer

King Charles III and Queen Camilla will mark 19 years of marriage on Tuesday, April 9, but other significances attached to that day, and the monarch's current health, could damper the happy occasion.

"April 9th is also the date of Prince Philip’s death, so it will be tinged with sadness," royal expert Richard Fitzwilliams told an outlet.

The former Duke of Edinburgh passed away on that day nearly three years ago, after long since having become the longest-serving consort of a monarch in British history. The passing of the King's "Dear Papa" also brought an end to a staggering 73.5 years of marriage between Philip and Queen Elizabeth II, who died 1.5 years later on September 8, 2022.

One royal insider later claimed that the late Queen "never truly got over losing Philip; she revealed to one of her spiritual advisors that widowhood was simply not for her." They added: "The late Duke of Edinburgh started jokes with the Queen as far back as the 1990s, teasing her about 'who will be here to correct your shoddy memory when I go?' and Her Majesty then lamented to the clergyman over how much she missed him."

The day will likely also be less joyous due to Charles III's cancer struggle, although it has been reported that the treatments he has been receiving for two months have created a "positive outlook."

Fitzwilliams added how the regal pair will likely mark April 9 "privately" but could release an official photograph of themselves for the anniversary. "The fact that he is suffering from a serious illness will bind them ever closer as she provides the pivotal emotional support he needs at this time," the expert revealed.

The King and Queen first met on a polo field in 1970 before embarking on a whirlwind romance. With rumors long-circulating that the then-Camilla Shand's suitability as a Princess of Wales was marked as a "no-go at the Palace," in addition to the future queen also having feelings for another, the duo parted ways. Camilla married Andrew Parker-Bowles in 1973, and the pair went on to have two children.

The Prince of Wales, who was serving in the British Armed Forces at the time, was left "utterly devastated" and totally "lovesick" over his "beloved" for years to come. He tried to distance his feelings for her by romancing and then marrying a 19-year-old Lady Diana Spencer in 1980 and 1981, but it wasn't to be.

Camilla and Andrew divorced in 1995 with the Prince and Princess of Wales following suit in 1996. With Diana's tragic death in 1997 "shaking the monarchy to its very foundations," the pair did not first appear as a couple in public until January 1999. With a slow but sure public acceptance growing year by year, they married in a registrar's office on April 9, 2005.

GBN reported on Fitzwilliam's comments.