While the Duke and Duchess of Cambridge and their son Prince George enjoyed a safe and happy Christmas with family this year in celebrations at Sandringham, Queen Elizabeth specifically requested for their dog Lupo to be left off of the guest list, the Telegraph reports.

Lupo, Kate Middleton and Prince William's beloved cocker spaniel, had to stay at the Middleton manor in Berkshire during the holidays, though the Duke and Duchess saw him after they had left the retreat in Norfolk, England on Boxing Day.

"The Duchess is especially fond of the puppy and was sad that he could not accompany them. He had to sit it out at her parents' home in Berkshire," a courtier told the Telegraph.

According to "dog whisperer" Roger Mugford, who has counseled the Queen previously on her own cocker spaniels, the decision was likely a wise one.

"Cocker spaniels are sociable by nature and good at getting along with other dogs, but the same isn't always true of the Queen's corgis," he told the newspaper. "The commotion of Christmas - the large number of people, the unfamiliar faces and all the distractions - can make them unpredictable. Another dog coming into their territory, with all of that going on, isn't necessarily going to be welcomed by them."

Last year, the Queen's unruly corgis allegedly "ganged up" on Princess Beatrice's Norfolk terrier, Max, a situation that was not worth repeating where Lupo is concerned. Her dogs have been known to be territorial and aggressive towards other dogs.

Lupo's behavior was probably not part of the reason, as he can be seen posing happily and peacefully with his dog parents and baby Prince George in their casual family portraits taken in Bucklebury, Berkshire, and appears gentle and well-behaved on a leash.

Click here to see candid photos of Kate Middleton playing in the park with Lupo.