He started his career competing in pony racing, before moving south at age 15 to join Mark Johnston's stable after e-mailing them asking if he could ride out for them.
[1] As a youngster, he played a lot of rugby, getting to the equivalent of county level, but he opted to stay in Scotland to go pony racing instead of going on tour to Wales with his club Hawick Albion.
In 2013, he passed 50 winners for the first time[3] to become Champion Apprentice, six years after Greg Fairley, another jockey from the Scottish border town of Hawick.
In 2021, he passed 100 winners - a target he and his agent had set at the start of the year[2] - and £1million in prize money for the first time and ended with his highest total to date - 105.
[3] In 2020, he established a hugely successful partnership with the John Quinn-trained filly Highfield Princess, riding her to victory in four minor races.
She took a major step forward the next year, giving Hart his first Royal Ascot winner in the Buckingham Palace Handicap, then taking the Queen Charlotte Fillies' Stakes.