 The King Charles Spaniel is less popular than the Cavalier in both the UK and the US . In 2010 , the Cavalier was the 23rd most popular breed , according to registration figures collected by the American Kennel Club , while the English Toy Spaniel was the 126th . In the UK , according to the Kennel Club , the Cavalier is the most popular breed in the Toy Group , with 8 @,@ 154 puppies registered in 2010 , compared to 199 registrations for King Charles Spaniels . Due to the low number of registrations , the King Charles was identified as a Vulnerable Native Breed by the Kennel Club in 2003 in an effort to help promote the breed . 
