Thought to have originated in East Asia, and possibly acquired by European traders via the Spice Road, early toy spaniels were first seen in Europe during the 16th century.

They became linked with English royalty during the rule of Queen Mary I (from 1553-1558), eventually earning their name after being made famous by their association with King Charles II.

Members of the breed were also owned by Queen Victoria (Dash) and her great-granddaughter Grand Duchess Anastasia Nikolaevna of Russia.

[2] The red and white variety of toy spaniel was first seen in paintings by Titian,[3] including the Venus of Urbino (1538), where a small dog is used as a symbol of female seductiveness.

He noted that dogs were a common gift and thought that the earlier voyage of Captain Saris introduced a Japanese type of spaniel into England.

[1] In the 17th century, toy spaniels began to feature in paintings by Dutch artists such as Caspar Netscher and Peter Paul Rubens.

French naturalist Georges-Louis Leclerc, Comte de Buffon would later describe these types of dogs as crosses between spaniels and Pugs.

Samuel Pepys' diary describes how the spaniels were allowed to roam anywhere in Whitehall Palace, including during state occasions.

[10] In an entry dated 4 September 1667, describing a council meeting, Pepys wrote, "All I observed there was the silliness of the King, playing with his dog all the while and not minding the business.

"[11][12] Charles' sister Princess Henrietta was painted by Pierre Mignard holding a small red and white toy-sized spaniel.

[13] Toy spaniels continued to be popular in the British court during the reign of King James II, through that of Queen Anne.

On Rover, a Lady's Spaniel, Jonathan Swift's satire of Ambrose Philips's poem to the daughter of the Lord Lieutenant, describes the features of an English toy, specifying a "forehead large and high" among other physical characteristics of the breeds.

The toy spaniels of this century weighed as little as 5 pounds (2.3 kg),[20] although they were thought to be the dog breed most prone to becoming overweight, or "fattened".

"[23] This idea was supported by Vero Shaw in his 1881 work The Illustrated Book of the Dog,[23] and by Thomas Brown in 1829 who wrote, "He is seldom used for field–sports, from his diminutive size, being easily tired, and is too short in the legs to get through swampy ground.

William Youatt in his 1845 study, The Dog, was not enamoured of the changes: "The King Charles's breed of the present day is materially altered for the worse.

By doing this, the dog's sense of smell was impaired, and according to 19th century writers, this caused the varieties of toy spaniel to be removed from participation in field sports.

[29] The first written occurrence of a ruby coloured toy spaniel was a dog named Dandy, owned by a Mr Garwood in 1875.

[35] Grand Duchess Anastasia Nikolaevna of Russia owned a King Charles Spaniel at the time of the shooting of the Romanov family on 17 July 1918.

Eight days later, Nicholas Sokolov of the White Forces found a clearing where he believed the bodies of the Romanov family had been burnt, and discovered the corpse of a King Charles Spaniel at the site.

[43][44] Elizabeth II has also owned King Charles Spaniels in addition to the dogs most frequently associated with her, the Pembroke Welsh Corgi.

Mark Evans, the chief veterinary advisor for the Royal Society for the Prevention of Cruelty to Animals (RSPCA), said, "Dog shows using current breed standards as the main judging criteria actively encourage both the intentional breeding of deformed and disabled dogs and the inbreeding of closely related animals";[46] this opinion was seconded by the Scottish SPCA.

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.

[49] 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.

[51] The King Charles has large dark eyes, a short nose, a high domed head and a line of black skin around the mouth.

[52] In addition, their facial features, while similar, are distinguishable: the Cavalier's ears are set higher and its skull is flat, while the King Charles' is domed.

[36] It is intelligent enough to be used for obedience work and, due to its stable temperament, it can be a successful therapy dog for hospitals and nursing homes.

[61] The eye problems associated with the King Charles Spaniel include cataracts, corneal dystrophy, distichia, entropion, microphthalmia, optic disc drusen, and keratitis.

Compared to other breeds, the King Charles Spaniel has an increased risk of distichia (where extra eyelashes or hairs cause irritation to the eye).

[67][68] The OFA conducted a survey on cardiac disease, where of 105 breeds, the King Charles Spaniel was found to be 7th worst, with 2.1% of 189 dogs affected.

[73] In another study conducted by the OFA, the King Charles Spaniel was the 38th worst of 99 breeds for patella luxation; of 75 animals tested, 4% were found to have the ailment.