Sarah Siddons was a "strong, lengthy, attractive"[2] bay mare with a white star bred in France by her owner, Meg Mullion's Ardenode Stud.
Le Levanstell was a representative of the Byerley Turk sire line,[4] unlike more than 95% of modern thoroughbreds, who descend directly from the Darley Arabian.
[6] On her three-year-old debut Sarah Siddons finished second in the seven-furlong Athasi Stakes at the Curragh in April, beaten three quarters of a length by Serenica.
A quarter of a mile from the finish she appeared to be struggling but stayed on under pressure and as the field entered the final furlong she was disputing the lead alongside Clover Princess, Krassata and Lady Singer.
On her first appearance in England, Sarah Siddons started 100/30 second favourite behind her fellow Irish challenger I've A Bee in a field of thirteen for the Yorkshire Oaks at York Racecourse in August.
[2] Although the filly had run well on good and firm ground Prendergast had insisted that the Sarah Siddons would be better suited by a soft surface, which she encountered for the first time in the Prix Vermeille at Longchamp Racecourse on 19 September.
At York in August she produced her best performance of the year when finishing fourth behind Relkino, Artaius and Orange Bay in the Benson and Hedges Gold Cup.
[7] In 1975, the independent Timeform organisation gave her a rating of 102 p (the p indicating that she was likely to make significantly more than usual improvement), twenty-six pounds behind their top-rated juvenile filly Theia.