On Sunday I shot some polo at the Guards' Polo Club in Windsor Great Park.
It is not an easy sport to photograph. The playing area (called the "Ground") is the size of five football (soccer) pitches. The action is very fast and unpredictable. One moment they are at the far end, almost out of view, and suddenly they are close. The right focal length can become the wrong focal length in a couple of seconds.
It was a lot of fun.