Prince William and Kate Middleton
Prince William and Kate Middleton didn't attend the Royal Ascot because he's in another engagement and she's on leave. Pictured: Prince William and Middleton attend the second day of Royal Ascot at Ascot Racecourse on June 15, 2016 in Ascot, England. Getty Images/Chris Jackson

The royals joined forces for the Royal Ascot, but Prince William and Kate Middleton were noticeably missing.

On Tuesday, Queen Elizabeth II, Prince Harry, Meghan Markle, Prince Edward, Sophie, Countess of Sussex, Princess Beatrice and Princess Eugenie were all present at the Royal Ascot. However, the Duke and Duchess of Cambridge missed it due to a prior engagement.

According to Town & Country, Prince William is in Liverpool for the International Business Festival, the largest business festival in the world. He is the event's patron for 2018. Middleton's husband congratulated thousands of delegates at the gathering for bringing together business people "to build networks and to share knowledge."

Meanwhile, Middleton is still on maternity leave. She is not expected to return to her royal duties until October.

"It is traditional for new royal mums to take a six-month break from official engagements," Larcombe told Harper's Bazaar. "The wedding doesn't count because it was a 'family affair' but other than that, she will pick and choose her engagements. If she wanted, Kate could disappear into the background until October!"

On Saturday, Prince William and Middleton also skipped his cousin's wedding. The Duke and Duchess of Cambridge missed Celia McCorquodale and George Woodhouse's nuptials for the same reason, but Prince Harry and Markle were present.

"Kate is on maternity leave reportedly until October," royal commentator Richard Fitzwilliams explained Prince William and Middleton's absence at the wedding. "Obviously events such as Meghan and Harry's wedding and Trooping the Colour were exceptions and Louis is expected to be christened in the summer."

Fitzwilliams added that the royal family is already represented by the Duke and Duchess of Sussex. "Harry and Meghan were there lending royal support to his cousin," Fitzwilliams added.

Middleton still has several months to look after her newborn, Prince Louis. The Duke and Duchess of Cambridge may also be preparing for their son's christening. According to an insider, the palace might make an announcement about the event at the end of the month or in July.

Prince William and Middleton will make a compromise on Prince Louis' christening. They will share photos of the event, but will still make the occasion a private affair.