Highclere won one minor race as a two-year-old but improved to win the 1000 Guineas at Newmarket Racecourse and Prix de Diane at Chantilly.
As a descendant of the broodmare Feola, Highclere came from the same branch of Thoroughbred family 2-f which produced Round Table, Pebbles and Aureole.
[1] The filly was named after Highclere Castle, the home of the Queen's racing manager, Lord Carnarnvon.
At the end of the season she was allotted a weight of 109 pounds in the Free Handicap, a rating of the best two-year-olds to have raced in Britain.
[5] It was believed that the course and distance of the Oaks would not suit Highclere, and so the filly was rerouted to the French equivalent, the Prix de Diane over 2100m at Chantilly.
[6] On their return from France Dick Hern and Joe Mercer were invited to dine with the Royal Family at Windsor Castle.
Highclere finished second, beaten two lengths by the French four-year-old filly Dahlia, who was winning the race for the second year.
Highclere produced several winners, the best of whom were the colt Milford[8] and the filly Height of Fashion, both of whom won the Princess of Wales's Stakes.