Oliver Bromby gained his first international experience in 2015 when he finished fourth in the 100-meter run at the Youth World Championships in Cali in 10.60 s , as well as at the subsequent Commonwealth Youth Games in Apia with 10.45 s. The following year he reached the semi-finals at the U20 World Championships in Bydgoszcz over 100 meters, in which he was eliminated with 10.37 s and took sixth place with the British 4 x 100 meter relay in 39.57 s. In 2017 he won the bronze medal over 100 meters at the U20 European Championships in Grosseto in 10.88 seconds and finished fourth in the relay in 39.67 seconds. In 2019 he won the silver medal behind the Swede Henrik Larrson at the U23 European Championships in Gävle in 10.24 seconds and did not finish in the relay in the final.
Personal best
100 meters: 10.22 s (+1.5 m / s) on June 5, 2019 in Lee Valley
60 meters (hall): 6.63 s, February 5, 2020 in Ostrava
200 meters: 21.32 s (+1.5 m / s), May 9, 2015 in Eton
200 meters (hall): 21.36 s, 14 February 2016 in Sheffield