Kerstin was a brown mare with no white markings bred by Con Burke, of Kilmore, Fethard[2] and reared at the Shanbally Stud in County Tipperary, Ireland.
Although she was always well-behaved on the track Kerstin was a very temperamental and stubborn horse in training: her regular jockey Stan Hayhurst described her as "a real cow".
Kerstin made progress in the 1956/1957 despite a defeat by her "cousin" Linwell at Hurst Park in October[7] and a disappointing effort in the Great Yorkshire Chase.
The race appeared to lie between Linwell, Kerstin and Pointsman before the mare sprawled on landing at the second last, badly hampering Pointman.
The favourite however, was the French-bred seven-year-old Mandarin who had won the inaugural Hennessy Gold Cup before taking the King George VI Chase.
She became the second mare to win after Ballinode and the second horse trained in the North of England to take the Gold Cup after Limber Hill two years earlier.
Kerstin returned to form in November 1959: carrying 164 pounds she won the Hennessy Gold Cup, holding off a strong finish from Brunel II.
In December she won again, defeating a strong field including Roddy Owen, Done Up and Oxo in the Imperial Leather Chase at Manchester Racecourse.