Tarquin McTavish (possibly)
The race was held at night in order to avoid attracting Muggle attention. Arriving in Rome at dawn, McTavish and Astolfi were seen racing toward the finish line at the Coliseum, but at that point, a violent confrontation between supporters of the two racers who were gathered there broke out. During the course of the fight, Astolfi was transformed into a chicken, and McTavish was hit with a knee-reversal hex. The conflict culminated in an explosion that left the Colosseum in ruins.
Thanks to Orabella Nuttley, who stepped forward and fixed a few columns with her Mending Charm, the damage to the Colosseum was undone by the time that the Muggles woken by the explosion finally showed up at the scene. All they found was a few strangely-dressed men attempting to calm the agitated Astolfi, who was still a chicken. What happened to McTavish is unknown, but it can be presumed that his knees were returned to facing the proper way.