Wikipedia
The Norfolk Trotter is an extinct horse breed once native to East Anglia and Norfolk, England. It was said to be "a large-sized trotting harness horse originating in and around Norfolk".
In 1542, King Henry VIII required the wealthy to keep a specified number of trotting-horse stallions. The breed was well established in Norfolk, and later became known as the Norfolk Trotter. The most influential sire in its history the half-bred stallion Shales (foaled 1755), also known as "Old Shales". Shales' Thoroughbred sire, Blaze (foaled 1733), was a son of the great racehorse Flying Childers (a descendant of the Darley Arabian, one of the three foundation sires of the Thoroughbred).
The Norfolk Trotter became the all-around travel horse in England at this time. In Yorkshire, the same breed was known as the Yorkshire Trotter. Both breeds were also known as roadsters. It is common to see the term Norfolk/Yorkshire Roadster/Trotter in breed-history books; regardless of the name, all are the same breed of horse. They were used under saddle as the quickest means of travel in areas where there were no established roads. The breed was known for its ability to carry a heavy man for great distances at speeds up to 16-17 mph. Trotting races (usually under saddle), were very popular in the early part of the nineteenth century and Norfolk Trotters excelled in them.
A Norfolk Trotter stallion, Bellfounder was imported to America in 1822, and he proved a major influence in the founding of the Standardbred by becoming the damsire of Hambletonian 10. Norfolk Trotters also strongly influenced today's modern Hackney horse.