She was from the third crop of foals sired by Harbinger, a British horse who was rated the best racehorse in the world in 2010 when he won the King George VI and Queen Elizabeth Stakes by eleven lengths.

Since retiring to stud in Japan his other foals have included Normcore, Blast Onepiece, Mozu Katchan (Queen Elizabeth II Cup) and Persian Knight (Mile Championship).

The filly was stepped up in class for the Grade 3 for the Fantasy Stakes at Kyoto Racecourse and came home third of the twelve runners, beaten one and a half lengths and a head by Mi Suerte and Show Way.

[7] Deirdre began her three-year-old season by running third in the Kobushi Sho at Kyoto in February and then finished second to Rising Reason in the Listed Anemone Stakes at Nakayama Racecourse in March.

In the Grade 1 Oka Sho at Hanshin Racecourse on 9 April she started at odds of more than 207/1 but exceeded expectations as she produced a strong late run to finish sixth behind Reine Minoru, beaten less than three lengths behind the winner.

[8] After winning the Yaguruma Sho at Kyoto on 7 May Deirdre finished fourth to Soul Stirring, Mozu Katchan and Admire Miyabi in the Yushun Himba two weeks later.

The other fifteen runners included Lys Gracieux (second in the Oka Sho), Mozu Katchan, Rabbit Run (Rose Stakes), Reine Minoru and Caribbean Gold.

She was angled to the left in the straight and produced a strong late run to take the lead inside the last 100 metres and win by one and a quarter lengths and a nose from Lys Gracieux and Mozu Katchan.

[11] On her final run of the year Deirdre ended her season in the Queen Elizabeth II Cup at Kyoto in November in which she was matched against older fillies and mare.

[13] On her first run of 2018 Deirdre took on male opposition and came home sixth behind the four-year-old colt Clincher in the Grade 2 Kyoto Kinen over 2200 metres on 11 February.

[16] After a late summer break Deirdre returned to the track for the Grade 2 Fuchu Himba Stakes at Tokyo on 15 October and started the 1.3/1 favourite ahead of ten opponents including Lys Gracieux, Soul Stirring, Jour Polaire (Victoria Mile), Crocosmia (winner of the race in 2017) and Frontier Queen.

With Lemaire in the saddle she raced towards the rear of the field before making steady progress in the straight and ran down Lys Gracieux in the final strides to win by a neck.

[19] Deirdre began her fourth season in the Grade 2 Nakayama Kinen over 1800 metres on 24 February when she started favourite but came home sixth of the eleven runners behind Win Bright.

On 19 June at Royal Ascot she started the 33/1 outsider of the eight runners for the Prince of Wales's Stakes and finished sixth behind Crystal Ocean in a race run on soft ground in heavy rain.

[27] In the Bahrain International Trophy at Sakhir, her final race before retirement, Deirdre was ridden for the first time by Hollie Doyle and finished eighth of fourteen runners.