Complex sentence: Over 450 polo matches are held at the park each season and the highlight of the polo season is the annual British Open Polo Championship, for the Gold Cup, sponsored for many years by Veuve Clicquot, and from 2015 by Jaeger-LeCoultre.
Split into simpler sentences: Over 450 polo matches are held at the park each season. The highlight of the polo season is the annual British Open Polo Championship, for the Gold Cup, sponsored for many years by Veuve Clicquot, and now by Jaeger-LeCoultre.