In Buckfastleigh, Devonshire, England, in 1960, a certain Miss Cox became aware of a curly tom cat living in a deserted tin mine near home. It therefore came as no surprise to her when one day a stray tortoiseshell female gave birth to a male curly-haired kitten. She considered him quite beautiful, with lots of curls and even ringlets on his tail. Delighted with her kitten, Miss Cox named him "Kirlee".

As Kirlee grew, Miss Cox contacted a Mr. Brian Stirling-Webb, who was working to establish the curly-haired "Rex" (after the curly-haired Rex rabbits) cats as a breed, and offered the use of Kirlee as an outcross, to help increase the size of the Rex gene pool. Mr. Stirling-Webb and the other rex breeders were indeed very excited to hear the news.

They persuaded Miss Cox to send them Kirlee to use with their rex program.

For the past ten years, the curly-haired "Rex" breed that was to become today's Cornish Rex had been quite the rage in England, and many English breeders had been eagerly working with these "poodle cats".

Kirlee was mated with several rex females and eagerly awaited the upcoming kittens. To everyone's surprise, the resulting kittens were all straight-haired! It was only after Kirlee was bred to two Cornish Rex variant queens (normal coated females carrying the Cornish Rex gene) producing only normal shorthair and semi longhair kittens that suspicions arose as to whether Kirlee was indeed the result of the same mutation. No further breeding took place with Kirlee until the only Cornish Rex female kitten bred by a member of the group was old enough to be mated to him.
Broughton Purly Queen - a cream and white, was bred to Kirlee in 1961 producing a litter of normal coated kittens proving beyond doubt Kirlee was the result of a quite separate and incompatible mutation.

The "Gene I" Rex cat became known as the Cornish Rex, due to their origin in Cornwall, England (quite close to Devonshire), and has a curly coat with no guard hairs, and awn hair that is difficult to distinguish from the down. The body type is somewhat reminiscent of the "oriental" breeds of cats (such as Siamese), and the head is comprised of a series of smooth oval shapes.

Kirlee and the "Gene II" Rex cats became known as the Devon Rex, and established a look and breed characteristics distinctly their own. The Devon's coat contains all three types of hairs, although somewhat modified, and has a larger and looser curl than the Cornish Rex. The body type is very different as well, stockier and more heavily built, with a broader and shorter head with lower ears, and the distinctive "pixie" or "elfin" that has come to be the hallmark of the Devon look.

The two Rex mutations were then developed independently of each other but, due to the scarcity of breeding stock and lack of breeders willing to become involved at this early stage, it was necessary to use the variants produced from the three litters by Kirlee out of the Cornish Rex line as well as a few other variant litters produced by breeding pedigree shorthair queens to Kirlee.

As a consequence all Devon Rex worldwide have a considerable amount of Cornish Rex ancestry. No other Rex mutation has been found to be compatible with Devon Rex. In 1967, Great Britain's Governing Council of the Cat Fancy (G.C.C.F) recognized the distinction between the two breeds, and wrote standards to allow each of them into competition as distinctive breeds of cat.