A reputation can be made easily, but real achievements have to be earned on the track.

At York on Wednesday, Australia proved his merit as a Coolmore champion in definitive fashion by winning the Juddmonte International Stakes. While hardly short on accolades, and with the English and Irish Derby already under his belt, the chestnut has still been burdened with the mantle of trainer Aidan O'Brien's "best ever" Flat horse since the latter part of his two-year-old days.

Dropping back to a mile and a quarter, Australia not only brushed aside the French Derby winner The Grey Gatsby by two lengths, but left experienced Group One-class elders Telescope and Mukhadram treading water on the exacting plain of the Knavesmire.

While Joseph O'Brien starved to his absolute minimum weight of 8st 12lb, it must concern connections of other leading protagonists that the jockey's father reported Australia to have been eating rather more substantially and had ballooned to as much as 20 kilograms heavier than he was at Epsom.

Sent off the 8-13 favourite, O'Brien tried to keep a lid on his mount at the rear of the field as stablemate Kingfisher pulled the sextet along until Mukhadram tried his usual trick of staking his claim early and hit the front with three furlongs left. It became starkly obvious Australia was going to enter calculations when he began making progress on the wide outside but it was still quite surprising how easily he made it as he powered away inside the final furlong.

"He was ready for a racecourse gallop, that was where he was at. His weight rose alarmingly in the last three weeks but the lads at home were very happy. He was a lot of kilos up on his Derby run - he was 15-20 kilos heavier - and that's a lot of weight. But Joseph said that leaving the paddock in the Derby he felt like he was a two- or three-year-old, but today leaving he felt like a five-year-old," said O'Brien snr.

"There's such prize-money here and it's such a prestigious race that it's very hard to gallop him at a racecourse rather than bring him here."

O'Brien leaves decisions on planning to owners Coolmore, but said: "We had in our head to come here and then Leopardstown (Irish Champion Stakes, September 13) if everything went well."

As Australia is so regally bred, by Derby winner Galileo out of Oaks heroine Ouija Board, he is a priceless asset to the Coolmore breeding operation. There would be a huge demand to see him back against Kingman in the QEII at Ascot (Racebets offer 13-8 against 4-9 Kingman) but he could head in a slightly different direction.

Owner Michael Tabor said: "You go for a Derby because there's nothing like a Derby, but the truth of the matter is taking him to a mile and a quarter shows the speed he's got, and Joseph said you take him back to a mile and it would be perfect for him. You'd have to say he has to be up there with the very best. In a perfect world he'll go for (Leopardstown) and maybe the English Champion. Maybe one more after that, I don't think so, but we'll play out one race at a time."

O'Brien also took time to praise his son, saying: "I can't tell you the massive part Joseph plays. He can do 8st 12lb but we don't like him doing it. We're quite happy for him to put overweight up when he does. In the big days we want Joseph to be on and this is one of them."

The man himself said: "He was a bit fresh, his first run back after a while, but it was never really in doubt."

Kevin Ryan was thrilled with The Grey Gatsby, and said: "You don't burden a champion jockey with instructions, and I knew Richard Hughes would have a plan. He gave him a fabulous ride. We've no excuses, the winner is a fabulous horse. The way he's finished it looks like he'll get a mile and a half, which opens up plenty of options. Hopefully he'll stay in training next year."

Telescope held on for third, and Harry Herbert, of owners Highclere Thoroughbred Racing, said: "He needs a mile and a half, it's as simple as that. He's run very well over a mile and a quarter behind two Derby winners. It's up to Sir Michael (Stoute) but I would have thought the Breeders' Cup would be the main objective now."