[2] Until 1913, there was no requirement for British racehorses to have official names,[3] and the horse who later became known as The Duchess competed in 1811 as Mr. W. Wilson's b. f. by Cardinal York, dam by Beningbrough.

Mr Wilson's filly made her first appearance at Catterick Bridge Racecourse on 30 March 1815 when she finished third in the one mile Yearling Stakes:[4] it was to be her only defeat of the season.

On the day following Filho da Puta's victory in the St Leger, Wilson's filly defeated three opponents in a sweepstakes over the Two-Year-Old course.

On 18 April at Catterick Bridge Duchess of Leven made her first appearance as a three-year-old when she defeated Windlass to win the Filly Stakes over one and a half miles.

On the following afternoon, Duchess of Leven began a six race winning sequence when she beat Woodpecker Lass, and five other fillies in a sweepstakes over one and a half miles.

After a two-month break, Duchess of Leven returned to York in August where she won a sweepstakes over one and three quarter miles from Mr Petre's bay filly.

On 23 September, The Duchess was one of a field of ten colts and three fillies to contest the forty-first running of the St Leger at Doncaster.

[10] Three days later, running over the St Leger course and distance, The Duchess won a sweepstakes for fillies, beating Wathcote Lass "in a canter".

Racing on extremely soft ground she finished second, beaten a head by Leopold in the four mile Richmond Gold Cup, with the favourite Filho da Puta in third.

[14] The Duchess did not race as a four-year-old until July, when she started favourite for the Gold Cup at Preston and finished third behind the six-year-old Doctor Syntax.

[15] On 10 September, The Duchess returned to Pontefract and won the Gold Cup for the second time, beating Mr Lambton's Silenus.

[23] At the next Newmarket meeting two weeks later, The Duchess failed to conceded seven pounds to Mr Fox's colt Merlin in a 300 guinea match over the same course.

The Duchess ended her racing career in October 1819 by running unplaced behind Otho and Doctor Syntax in the Richmond Gold Cup.