stock had become critically rare by World War I. At least partially to alleviate this, British Shorthair breeders mixed Persians into their bloodlines. The genes thus introduced would eventually become the basis for the British Longhair. At the time, any long-haired cats produced were placed into the Persian breeding program. As all cats with the blue colouration were then judged together as variants on a de facto single breed. The Blue Shorthair, outcrossings of the British with the Russian Blue were also common. After the war, in an attempt to maintain the breed standard, the GCCF decided to accept only third-generation Persian/British Shorthair crosses. This contributed to another shortage of pure breeding stock by World War II, at which point the Persian and Russian Blue were reintroduced into the mix. British Shorthair breeders also worked with the French Chartreux, another ancient breed, which although genetically unrelated to the British Blue, is a very similar cat in appearance. Breeders worked to re-establish the true British type, and by the late 1970s, the distinctive British Shorthair had achieved formal recognition from both the Cat Fanciers' Association (CFA) and The International Cat Association (TICA). According to the GCCF's 2013 registry data, it is once again the most popular pedigreed breed in its native country. Description Appearance The British Shorthair is a relatively powerful-looking large cat, having a broad chest, strong thick-set legs with rounded paws and a medium-length, blunt-tipped tail. The head is relatively large and rounded, with a short muzzle, broad cheeks (most noticeable in mature males, who tend to develop prominent jowls) and large round eyes that are deep coppery orange in the British Blue and otherwise vary in colour depending on the coat. Their large ears are broad and widely set. The British Blue variant can often be confused with the grey Scottish Fold, a breed closely related to the British Shorthair. However, the Shorthair can be characterised by having its pointy triangle ears, whereas the Fold has softer, folded ears. They are slow to mature in comparison with most cat breeds, reaching full physical development at approximately three years of age. Unusually among domestic cats they are a noticeably sexually dimorphic breed, with males averaging and females . Coat, colour, and patterns The British Shorthair's coat is one of the breed's defining features. It is very dense but does not have an undercoat; thus, the texture is plush rather