King Charles was missing from Wednesday’s Royal Ascot due to his ongoing treatment for an undisclosed form of cancer.

With his absence confirmed, eagle-eyed fans spotted a subtle change at the annual event because he wasn’t there.

Taking to social media, one fan pointed out that a flag used at the event was the Ermine Border – which is typically used when the Consort is representing the Firm, and doesn’t have their own Royal Standard. Though the fan appeared to question why this specific flag was used, given that Camilla does have her own Standard.

The tweet read: “The bordered Royal Standard for Queen Camilla. The border is ermine, dontyaknow – usually for wives who don’t have their own Standard … yet Camilla does…”

The pair were joined by the Earl and Countess of Halifax in the carriage procession.

King Charles, who revealed his cancer diagnosis back in February, instead focused on holding audiences at Buckingham Palace as he continued to undergo cancer treatment.

The Queen and William were joined by other members of the Royal Family – including the Princess of Wales’s parents, Carole and Michael Middleton.

The Duke and Duchess of Edinburgh, who were celebrating their 25th wedding anniversary on Wednesday, were also present.

Princess Eugenie was joined by her husband Jack Brooksbank at Wednesday’s event, as well as Princess Beatrice and her husband, Edoardo Mapelli Mozzi.

Princess Anne was spotted with daughter Zara Tindall and her husband former rugby international, Mike Tindall.

Duchess Sophie was also joined by her father, Christopher Rhys-Jones.

The Duchess of York – who is Prince Andrew’s ex-wife and Princesses Eugenie and Beatrice’s mum – was also in the parade ring.

After her appearance at Trooping the Colour last weekend, the Princess of Wales was noticeably absent from Royal Ascot.

Princess Kate is undergoing preventative chemotherapy treatment since her cancer diagnosis earlier this year.

In a statement on Friday, Kate revealed that she is making “good progress” in her treatment but said that she has “good days and bad days”.