The heartwarming slideshow revisited some of the royal family’s milestones in 2017 but supporters noticed a glaring hole in the montage: the announcement that Prince William and the Duchess of Cambridge are expecting their third child in April. 

Highlights included Prince George starting school and the Duke of Cambridge's last shift as an air ambulance pilot in July.

The video also featured the engagement announcement of Prince Harry and Meghan Markle and the family watching the Trooping the Colour in June. 

But eagle-eyed fans noticed the absence of the Duke and Duchess of Cambridge pregnancy announcement. 

The couple announced in September they were expecting their third child and royal supporters were quick to comment on the omission. 

Instagram User Jennifer Marie Davis commented: “What about the announcement of the Duke and Duchess expecting third baby?!”

Another posted: “How about Kate's new pregnancy? Not a highlight?”

Jane Redmond said: “How could the Kensington Palace account make four of these year end retrospectives and not once include the fact that the Duke and Duchess of Cambridge are expecting in April? What a strange oversight!”

The highlight reel also included Charlotte and George taking part in their aunt Pippa’s wedding and the Sunken Garden at Kensington Palace being transformed into a White Garden in memory of Princess Diana. 

While some criticised the montage for the missing memory, others were delighted with the clips. 

Debi Coiro gushed: “New baby, a wedding, how wonderful! I love watching 'what comes next' in their lives. Prince Harry and Ms. Markle seem so united as partners in life; can't wait to see what's next for them.”

Another commented: “Thanks for sharing! I've enjoyed each of these milestones. Happy New Year!”