During her racing career she carried the green, blue and white colours of Lael Stable and was trained by William Haggas at Newmarket, Suffolk.
[2] One Master's dam Enticing was a top class sprinting mare who won the King George Stakes as a four-year-old in 2008,[3] and was a daughter of the 2000 Cartier Champion Two-year-old Filly Superstar Leo.
In September she was ridden by Ryan Moore when she started the 4/11 favourite for a similar event at Yarmouth Racecourse and recorded her first success as she took the lead a furlong from the finish and pulled away from her seven opponents to win by two and three quarter lengths.
At the end of the month the filly returned to Ireland for the Fairy Bridge Stakes over seven and a half furlongs at Tipperary Racecourse and started the 9/2 second favourite behind the Aidan O'Brien-trained I Can Fly.
Ridden by Colm O'Donoghue she recorded her first win of the year as she produced a strong late run to take the lead in the closing stages and won by half a length from Dan's Dream.
[8] On 7 October One Master was ridden by Pierre-Charles Boudot when she started a 33/1 outsider for the Group 1 Prix de la Forêt over 1400 metres at Longchamp Racecourse.
In November she was sent to the United States to contest the Breeders' Cup Mile at Churchill Downs and finished fifth to Expert Eye, a length behind the winner after staying on well in the closing stages.
In December she ended her campaign in the Hong Kong Mile at Sha Tin Racecourse, coming home eighth of the fourteen runners behind Beauty Generation.
Starting a 20/1 outsider for the Queen Anne Stakes at Royal Ascot in June she took the lead a furlong out but was overtaken in the closing stages and came home third behind Lord Glitters and Beat The Bank.
In the Falmouth Stakes at Newmarket Racecourse on 12 July she produced a sustained run from the rear of the field but failed by a neck to overhaul the Michael Stoute-trained four-year-old Veracious.
[11] She was dropped back in distance for the Prix Maurice de Gheest over 1300 metres at Deauville Racecourse in August and came home fifth behind the three-year-old Advertise.
[13] As Haggas predicted, One Master ended her season in the British Champions Sprint Stakes on 19 October and started the 4/1 joint-favourite alongside Advertise.
[14] The 2020 flat racing season in Britain was disrupted by the COVID-19 pandemic and One Master did not return to the track until 20 June when she contested the Diamond Jubilee Stakes, run behind closed doors at Royal Ascot, and finished sixth, beaten three and a half lengths by the winner Hello Youmzain.
Ridden for the first time by Tom Marquand, she had considerable trouble in running before squeezing through on the inside, catching the Irish three-year-old Valeria Messalina on the line and winning by a short head.
On 4 October, with Boudot in the saddle, One Master attempted to become the first horse to win the Prix de la Foret for a third time and started the 2.9/1 second favourite behind Earthlight.