During her racing career she carried the red and green colours of the Pall Mall Partners and was trained by Richard Hannon Jr. at Everleigh in Wiltshire.

She was the second foal of Coplow, a mare who failed to win in eight races but made a promising start to her broodmare career by producing the Upavon Fillies' Stakes winner Billesdon Bess.

In a very rough race she was denied a clear run until the final furlong but then produced a strong finishing burst to win by a head from her stablemate Cheeky Rascal.

[7] The Prestige Stakes at Goodwood on 26 August saw Billesdon Brook stepped up to Group 3 class and start the 4/1 second favourite behind the John Gosden-trained Verandah.

After being restrained by Levey in the early stages she began to make rapid progress in the last quarter mile, caught Whitefountainfairy 100 yards out and won by three-quarters of a length.

"[9] On her final appearance of the year she finished fifth in the Group 2 May Hill Stakes at Doncaster Racecourse but was only three and a half lengths behind the winner Laurens (later to take the Fillies' Mile).

On 18 April Billesdon Brook began her second season in the Nell Gwyn Stakes (a major trial race for the 1000 Guineas) over seven furlongs at Newmarket Racecourse.

Richard Hannon admitted that the filly was not the best fancied of his three runners in the race but insisted that there was "no fluke" about her victory while Levey said "She ran "gassy" in the Nell Gwyn.

The filly was then stepped up in distance for the ten-furlong Nassau Stakes at Goodwood and finished fourth again, beaten three and a half lengths by the winner Wild Illusion.

On her first appearance as a four-year-old Billesdon Brook contested the Group 2 Dahlia Stakes over nine furlongs at Newmarket on 5 May and finished a well-beaten third behind Worth Waiting and Nyaleti in a five-runner field.

Thirteen days later at Newbury Racecourse she was matched against male opposition in the Group 1 Lockinge Stakes and came home ninth behind the six-year-old gelding Mustashry at odds of 33/1.

After racing in mid-division she made progress in the last quarter mile, took the lead 100 yards from the finish and won by a length from Crossing The Line to record her first success for over a year.

[14] Three weeks after her win at Chelmsford Billesdon Brook attempted to follow up in the Pipalong Stakes over one mile at Pontefract Racecourse but after taking the lead 50 yards from the finish she was caught in the final strides by the 25/1 outsider Exhort and beaten three quarters of a length into second place.

[19] Billesdon Brook began her five-year-old season in the Listed Snowdrop Fillies' Stakes over one mile on the Polytrack surface at Kempton Park on 3 June, and led until the final furlong before finishing second by three quarters of a length to Nazeef.

In October Billesdon Brook ran for the third time in the Sun Chariot Stakes but failed to reproduce her 2019 form as she came home eighth of the twelve runners behind Nazeef, beaten five and three quarter lengths by the winner.