A native of Wales, the Sealyham Terrier was developed by crossing the Dandie Dinmont Terrier, West Highland Terrier, Corgi, Wirehaired Fox Terrier and the Bull Terrier. It derived its name from the Sealyham Estate of the breeder, Captain John Edwardes. It was once one of the more popular terrier breeds but now they are listed as among the most endangered breeds in Wales when banner digs have been banned in the area. Bred to stand low to the ground, its prescribed height should be no more than 12 inches and the maximum weight should be 20 pounds. It has a long head and body, a moderate stop and a black nose with large nostrils. The eyes are oval shaped, wide set and dark in colour. Its tail is normally docked (even though docking tails is considered illegal in most parts of Europe) and carried high. The weather resistant coat is wiry and typically in solid white. Sometimes it presents with lemon, tan or badger-coloured marking on the head and ears.
The Sealyham Terrier was developed as a hunting breed but is now kept as a house companion. They are affectionate, loving, loyal and spirited. They are actually fairly active dogs however if they are not given enough regular activity and kept mostly indoors they become relatively inactive, or as some put it “couch potatoes.” They are good with older children and other pets but are somewhat reserved towards strangers and are not as rowdy as the other terrier breeds. They shed little to no hair and prefer cooler climates.