A betting coup goes wrong?

Bath races for 1771 open with a 50 guinea plate, competed for by four horses, including Dennis O'Kelly's bay horse Humble which started as evens favourite but with very few people willing to take those odds.

Dennis O'Kelly 1773
Note the severely cropped tail and ears of the horse
typical for the period.

The first heat went to Mr Clarke's brown horse Valentine by a good margin, with Humble trailing in last. This shifted the odds considerably 5 to 4 being offered for Valentine against the field.

The second heat was suspiciously very different. Humble led from the off and, whipped on by his jockey, stayed ahead of the field until they reached the distance post 240 yards from the finish when Valentine slipped passed him. The two horses completed the race neck and neck, but ultimately victory went to Valentine.

Given O'Kelly's reputation as a professional gambler and pimp and his known history of rigging the results of sporting events, the suspicion must be that this was a betting coup which went wrong.