At the First Spring Meeting at Newmarket in May, Gustavus won the Newmarket Stakes, beating the colts Tressilian and Fleur de Lis.

In his second start of the season, Gustavus ran in the Derby Stakes at Epsom against a field of twelve other horses.
Gustavus was the betting favorite for the running, starting the race with 2 to 1 or 7.5 to 4 odds depending on the bookmaking operation.
The Duke of Grafton's colt Reginald (the winner of the 2,000 Guineas Stakes) initially took the lead and "made the running" with Gustavus initiating "some play" with Reginald at Tattenham Corner and the two horses "worked together from end to end in the Derby, as if it was run a match."
Gustavus was ridden by Sam Day and Reginald's jockey was Francis Buckle.
Buckle's "nerve rather went" while Day "kept close to his girths," allowing Gustavus to overtake Reginald in the final stretch to win the race by half a length.
Reginald finished second and the colt Sir Huldibrand third.
Day described the finish graphically: "We wound in and out, for all the world like a dog at a fair."
Gustavus was the first grey horse to win the Derby and one of only four grey horses to win the event.
Hunter reportedly won "a very considerable sum" by betting on Gustavus in the Derby, while two brothers reportedly "lost twenty-six thousand pounds" between them but "handsomely paid the debt" when it was due.
The 1821 Derby was portrayed in a painting (right) by French artist Théodore Géricault.
The depicted, dramatized scene occurred shortly before the race finish, with Gustavus in third place following closely behind the frontrunner Reginald.

Gustavus was unplaced in the St. Leger Stakes run on 17 September at Doncaster, which was won by the colt Jack Spiggot.
A few days later, Gustavus finished second to the filly My Lady in the 1000-guinea Gascoigne Stakes run over the St. Leger course.
The third runner and the betting favorite in the race, a colt named Sandbeck, was disqualified after running into a post and falling.
At the Houghton meeting on 29 October, Gustavus won a mile-long, 150-guinea match race against Mr. Fox's horse Pancha, and a few days later, Gustavus won 200 guineas after beating Lord Exeter's unnamed colt sired by Androssan in a match race.
At the First Spring Meeting at Newmarket in May, Gustavus won the Newmarket Stakes, beating the colts Tressilian and Fleur de Lis.
In his second start of the season, Gustavus ran in the Derby Stakes at Epsom against a field of twelve other horses. Gustavus was the betting favorite for the running, starting the race with 2 to 1 or 7.5 to 4 odds depending on the bookmaking operation. The Duke of Grafton's colt Reginald (the winner of the 2,000 Guineas Stakes) initially took the lead and "made the running" with Gustavus initiating "some play" with Reginald at Tattenham Corner and the two horses "worked together from end to end in the Derby, as if it was run a match." Gustavus was ridden by Sam Day and Reginald's jockey was Francis Buckle. Buckle's "nerve rather went" while Day "kept close to his girths," allowing Gustavus to overtake Reginald in the final stretch to win the race by half a length. Reginald finished second and the colt Sir Huldibrand third. Day described the finish graphically: "We wound in and out, for all the world like a dog at a fair." Gustavus was the first grey horse to win the Derby and one of only four grey horses to win the event. Hunter reportedly won "a very considerable sum" by betting on Gustavus in the Derby, while two brothers reportedly "lost twenty-six thousand pounds" between them but "handsomely paid the debt" when it was due. The 1821 Derby was portrayed in a painting (right) by French artist Théodore Géricault. The depicted, dramatized scene occurred shortly before the race finish, with Gustavus in third place following closely behind the frontrunner Reginald.
Gustavus was unplaced in the St. Leger Stakes run on 17 September at Doncaster, which was won by the colt Jack Spiggot. A few days later, Gustavus finished second to the filly My Lady in the 1000-guinea Gascoigne Stakes run over the St. Leger course. The third runner and the betting favorite in the race, a colt named Sandbeck, was disqualified after running into a post and falling. At the Houghton meeting on 29 October, Gustavus won a mile-long, 150-guinea match race against Mr. Fox's horse Pancha, and a few days later, Gustavus won 200 guineas after beating Lord Exeter's unnamed colt sired by Androssan in a match race.
Gustavus (horse)