JOSEPH O’Brien insists he would have no qualms about taking on the best over a mile once more with Australia following his thrilling victory in Saturday’s Investec Derby.

The Aidan O’Brientrained colt was narrowly denied by Night Of Thunder and Kingman in the 2000 Guineas at Newmarket on his penultimate start and took the step up to a mile and a half in his stride with a dominant display at Epsom.

Night Of Thunder and subsequent Irish 2,000 Guineas winner Kingman look set to lock horns again in the St James’s Palace Stakes at Royal Ascot and while Australia is highly unlikely to turn up in Berkshire following his Derby romp, O’Brien jnr would be confident of beating both in a rematch.

He said: “When we heard about the forecast for Saturday, we’d have had no qualms about taking him out and taking on the other two horses (Night Of Thunder and Kingman) in the St James’s Palace. I would have really fancied him to win.

“We’ll never know if I’d been drawn with the other horses whether I’d have beaten them or not (in the 2000 Guineas), but I certainly think I would.

“He’s got a serious amount of pace. We’ve made no secret of that.

He definitely has sevenfurlong pace – no doubt.

I travelled as well as anything in the Guineas.

“I was cantering throughout the whole race yesterday and you can literally ride the horse any way.

He’s very uncomplicated.”

The jockey admitted the rain-softened ground and the step up in trip were minor concerns prior to the premier Classic, but those worries soon evaporated once the stalls opened.

O’Brien told At The Races: “It’s an unbelievable feeling (to win the Derby).

“I only had two concerns really. One was the ground, but once we’d walked the track we were quite happy.

A lot of the rain that had been forecast didn’t come.

“The second (concern) was the mile and a half.

He shows a lot of speed and his run in the Guineas was a massive run in what was probably a very good Guineas.

“He’s got a very good attitude and relaxes well.”

Australia was O’Brien’s second Derby winner following the similarly impressive display of Camelot two years ago, a horse who had previously won the Guineas and came mighty close to completing the Triple Crown in the St Leger.

“They’re two very good horses. I suppose formwise there was a bit more depth to the Derby this year,” said the jockey.