After showing promising, but unexceptional form in 1958, she improved to be the British Horse of the Year in 1959, winning all six of her races, including the Classic 1000 Guineas and Epsom Oaks.
As a descendant of Mumtaz Mahal, Petite Etoile was a member of the same branch of Thoroughbred family 9-c which produced Shergar, Oh So Sharp and Risen Star.
Doug Smith was later to admit that he had kept quiet about the feel Petite Etoile had given him in the Free Handicap in the hope that Piggott would choose one of Murless's two other contenders Collyria or Rose of Medina and that he would keep the ride.
The favourite was the undefeated Cantelo, a filly whose wins included the Royal Lodge Stakes against colts and who was regarded as a superior stayer, whereas Petite Etoile's pedigree led to doubts about her stamina over one and a half miles.
On her final start of the year she contested the Champion Stakes at Newmarket[9] and won by half a length from the previously unbeaten Irish St Leger winner Barclay with the French-trained Javelot in third.
[10] On Petite Etoile's 1960 debut she won the Victor Wild Stakes over ten furlongs at Kempton Park Racecourse.
Starting at odds of 1/3 she was restrained by Piggott until the closing stages where she displayed "devastating speed",[11] to accelerate past Parthia, "as if he were a selling plater" and win by one and a half lengths.
[13] In the King George VI and Queen Elizabeth Stakes at Ascot in July, Petite Etoile started 2/5 favourite, despite the rain-softened ground.
Petite Etoile then succumbed to the epidemic of coughing which affected many British racing stables, and missed the rest of the season, leading to reports that she would be retired.
Petite Etoile was then moved back up to one and a half miles for the Aly Khan International Memorial Gold Cup, named after her late owner, in which she finished second to High Hat.
Later in the same month she was beaten half a length by Le Levanstell when starting 2/9 favourite for the Queen Elizabeth II Stakes at Ascot.
Petite Etoiles career earnings of £72,624 set a record for a female racehorse trained in Britain or Ireland, which stood until it was surpassed by Park Top in 1969.