With the intention to develop the best all-round, working Terrier, Captain John Owen Tucker Edwardes began a selective breeding program at his estate at Sealyham, Pembrokeshire, crossing the Welsh Corgi, the West Highland White Terrier, and the Bull, Fox and Dandie Dinmont Terriers. The result was a dog distinctive in appearance and structure, with a specialism in driving out den quarry for the hunter to kill. This versatile breed was also widely utilised in pest control and small game hunting, with its white coat distinguishing it from the prey. Originally developed over 150 years ago, the Sealyham Terrier was first shown at a dog show in 1903, and became particularly popular following WWI. Famous figures to have owned a Sealyham include Humphrey Bogart, Elizabeth Taylor and Agatha Christie. Despite once being one of the most popular Terrier breeds, the Sealyham is now considered rare, being listed as a Vulnerable Native Breed by the Kennel Club.
A dog of compact size and structure, the Sealyham Terrier boasts short legs, a rectangular body, a deep, square-cut muzzle, a tapering tail, and dark, almond-shaped eyes. The double coat is typically dense, with a hard, wiry texture. It is always observed in white with facial markings in brown, black or lemon. The Sealyham usually has a beard, or feathering on the face and muzzle. Despite being distinctive amongst the Terrier breeds, the Sealyham is sometimes mistaken for the soft-coated Wheaten Terrier or the West Highland White Terrier. Rustic in appearance and dogged and fearless on the hunt, the Sealyham has established a concrete reputation for itself as an all-purpose, sporting dog.
Characteristically more mellow than its Terrier cousins, the Sealyham is well suited to relaxed domestic living. Adapted for town or country life, the Sealyham possesses a gentle, amiable temperament and does not require strenuous exercise. The Sealyham is vigilant to change and threat and highly territorial, making an excellent watch dog. Otherwise, a Sealyham will remain calm and affectionate, rendering it the ideal breed choice for active families, being compatible with children and engaging well in exercise and play. In order to avoid wilful, disobedient or aggressive behaviours, early socialisation, firm leadership and consistent training is important and beneficial. On average, a healthy Sealyham Terrier will weigh 8-9 kg, with a life expectancy of 15 years.
Generally very healthy and long-lived, the Sealyham Terrier is prone to few breed-specific disorders. Those it is susceptible to include optical lens luxation, and canine degenerative myelopathy, a progressive disease of the spinal chord.