Buick is quick to broaden his horizons after stunning St Leger triumph

As he celebrated his fifth Group One victory in a fifth different country in the past year by donning the cap that is traditionally presented to the victorious St Leger rider, the fresh-faced 22-year-old contemplated even bigger prizes.

"You say winning a Classic so young is not a big deal, but it is," he told the Yorkshire Post after winning the Doncaster showpiece at the first attempt. "It's very special. Next, the Derby."

The one-time Northern Racing College graduate smiled continuously as he recounted his winning ride on the Breeders Cup-bound Arctic Cosmos.

His mentor Frankie Dettori, well-beaten on the red-hot favourite Rewilding, wandered across the Doncaster paddock and put his arm around Flat racing's rising star.

"I can tell it hasn't sunk in yet," Dettori said as he looked into the young pretender's eyes and gave Buick's cherubic face a friendly slap. "He's in a daze."

Dazed or not, ice-cool Buick won a highly-competitive nursery aboard top weight Buthelezi – the raw two-year-old only hit the front in the final stride – before winning the finale on Senate to complete a momentous 115-1 hat-trick. He then flew to France and won the valuable Qatar Prix Foy at Longchamp with a masterful front-running ride on Duncan. The Prix de l'Arc de Triomphe, Europe's richest race, is next.

These successes explain why Buick is highly-regarded; he retained his focus after the biggest success of his career.

All four weekend winners were trained by John Gosden, a man instrumental in Dettori's career during the Italian's formative years. The trainer's stable is so powerful that Buick is content to take an occasional day off from racing – as he revealed in Saturday's Yorkshire Post – if it helps retain his mental sharpness for the major races.

As such, the 2010 St Leger will be remembered by racing historians as Buick's first Classic, and surely one of many, rather than for the equine guile of the relentless galloper Arctic Cosmos who benefited from the application of blinkers to improve his concentration. "He's been dossing all year, he's still a big baby," added Buick.

The St Leger triumph also vindicated Gosden's decision last winter to recruit Buick in place of Jimmy Fortune.

"William is very mature for a young man," said Gosden. "We are living in a world of celebrity froth which can be very destructive for young athletes – footballers, boxers, jockeys etc."