Puerto Rico

The penny dropped at Doncaster in September. Stepped up to seven furlongs for the first time, he won — and won a Class 1 race, which is about as good as it gets on the British racing calendar. O'Brien's verdict afterwards was blunt and enthusiastic: a lovely, big, powerful, mature horse with loads of speed. The form stacked up quickly too. The horse that finished third that day went out and won the very next day, which made Puerto Rico's victory look even more impressive in hindsight.

After Doncaster, the team considered a trip to the Breeders' Cup in America, but when stablemate Gstaad took that slot, Puerto Rico was sent instead to Saint-Cloud in France, where he stepped up to a mile. O'Brien came away convinced he had found the horse's proper trip. Pacey enough to burn off rivals, but relaxed enough in his races to potentially get even further as he matures — that is a rare combination, and it is exactly what trainers dream of finding in a horse heading into their Classic season.

That Saint-Cloud run was seven months ago. Puerto Rico has won just 1 of his 6 races in total, which on paper looks modest, but the context matters enormously: he spent most of last year running over a distance that was too short, still managed to place four times, and the moment he was given the right conditions he won at the highest level. He heads into the new season pointed at the Guineas — Britain's premier race for three-year-olds over a mile — and on the evidence so far, he is exactly the kind of horse that race was made for.