Horse's age Flat race horses see the track much earlier than their National Hunt counterparts, who generally have to negotiate jumps and longer distances.
The English Classics - the 1,000 and 2,000 Guineas, the Oaks, the Derby and the St Leger - are open to three-year-olds only.
Horses must be aged over five to run in the Grand National, and some veteran runners are still competing aged 13.
