Enstone Spark is a Thoroughbred

Thoroughbred

The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...

 filly

Filly

A filly is a young female horse too young to be called a mare. There are several specific definitions in use.*In most cases filly is a female horse under the age of four years old....

racehorse

Horse racing

Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...

 best known for winning a British Classic Race.

Trained by Barry Hills

Barry Hills

Barry Hills is a British thoroughbred horse trainer. He lives in Lambourn, England.-Biography:Barry Hills had three sons in his first marriage: John, Michael, and Richard. John is a horse trainer, and both Michael and Richard are jockeys. After his divorce, he married Penny Hills, and had two more...

, at age two, Enstone Spark won the 1977 Lowther Stakes

Lowther Stakes

The Lowther Stakes is a Group 2 flat horse race in Great Britain open to two-year-old thoroughbred fillies. It is run at York over a distance of 6 furlongs , and it is scheduled to take place each year in August.-History:...

 at York Racecourse

York Racecourse

York Racecourse is a horse racing track in the southwest of the city of York in North Yorkshire, England with a spectator capacity of 60,000. The most famous race to be held at York on an annual basis is the Ebor Handicap, which is run during the Ebor Festival meeting in August...

. http://www.independent.co.uk/sport/racing-cape-verdi-can-boost-her-guineas-claims-1246562.html In 1978, her Canadian

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 owner, Dick Bonnycastle

Richard A. N. Bonnycastle

Richard Arthur Northwood Bonnycastle is a Canadian businessman who is the former owner and publisher of Harlequin Enterprises and an owner of Thoroughbred racehorses...

, was planning to ship Enstone Spark to race in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 but an outbreak of contagious equine metritis

Contagious equine metritis

Contagious Equine Metritis is a venereal infection of the genital tract of horses brought on by the Taylorella equigenitalis bacteria. Passed on through sexual contact, according to Robert N. Oglesby DVM, the disease was first reported in 1977 on horse breeding farms in England and was found in...

 forced a change of plans and she remained to compete in England.

In 1978 Enstone Spark earned the most important win of her career at Newmarket Racecourse

Newmarket Racecourse

The town of Newmarket, in Suffolk, England, is the headquarters of British horseracing, home to the largest cluster of training yards in the country and many key horse racing organisations. Newmarket Racecourse has two courses - the Rowley Mile Course and the July Course. Both are wide, galloping...

 with a victory in the Classic 1,000 Guineas Stakes at a time when she was still more than a month shy of her third birthday.

Retired from racing a winner of five races with three second-place finishes in her two years of racing, Enstone Spark was assigned to broodmare duty. Bred to stallions

Stallion (horse)

A stallion is a male horse that has not been gelded .Stallions will follow the conformation and phenotype of their breed, but within that standard, the presence of hormones such as testosterone may give stallions a thicker, "cresty" neck, as well as a somewhat more muscular physique as compared to...

 such as Affirmed

Affirmed

Affirmed was an American Thoroughbred racehorse who was the eleventh and most recent winner of the United States Triple Crown of Thoroughbred Racing...

, Roberto

Roberto (horse)

Roberto was an American-bred Thoroughbred Champion racehorse who competed in Ireland and England.-Background:Roberto was bred by Galbreath at his Darby Dan Farm near Lexington, Kentucky. The son of the successful sire Hail To Reason out of the dam Bramalea, Roberto's grandsire was Turn-To, a...

, and Bold Forbes

Bold Forbes

Bold Forbes was a champion thoroughbred racehorse, winner of the 1976 Kentucky Derby and Belmont Stakes.-Beginnings:...

, her offspring were not successful in racing.
http://www.independent.co.uk/sport/general/birth-dates-a-guide-to-derby-destiny-713751.html