The English Mastiff is a breed of large dog. The English Mastiff is a breed of large dog. National kennel clubs, including the United Kingdom's Kennel Club and the American Kennel Club, refer to the breed as simply the Mastiff. They perhaps descended from the ancient Alaunt and Pugnaces Britanniae, with a significant input from the Alpine  Mastiff in the 19th century. Distinguished by its enormous size, massive head, short coat in a limited range of colours, and always displaying a black mask, the Mastiff is noted for its gentle and loving nature. The ancient Roman poet Grattius (or Grattius Faliscus) wrote of British dogs, describing them as superior to the ancient Greek Molossus, saying: The Mastiff is a particularly large dog demanding correct diet and exercise. Excessive running is not recommended for the first two years of the dog's life, in order not to damage the growth plates in the joints of this heavy and fast-growing dog, which in some weeks may gain over 5 lb.