Aidan O'Brien is wary about the prospect of soft ground at Epsom next Saturday for Investec Derby favourite Australia.

The Galileo colt has been all the rage for the premier Classic since his close-up third in the 2000 Guineas at Newmarket on 3 May.

However, Australia has not yet been tested in demanding conditions, with his trainer hoping the recent wet spell quickly recedes.

O'Brien said: "We wouldn't like the ground to be soft.

"He's a beautiful moving horse, everybody saw the class he showed at Newmarket.

"Obviously soft ground wouldn't be ideal, but we'll have to wait and see and hope it's not."

O'Brien confirmed at the 'Breakfast with the Stars' morning at the Surrey venue on Thursday that Australia may be accompanied by Geoffrey Chaucer, Kingfisher and Orchestra.

Joseph O'Brien, the trainer's son, is set to partner Australia, while Ryan Moore, who won the Irish 1,000 Guineas last weekend aboard the stable's Marvellous, is poised to get the leg-up on Geoffrey Chaucer.

The latter has this week been well backed in the Derby market after rumours circulated of the colt having beaten Australia in a gallop at Ballydoyle.

O'Brien said: "I don't know where these (rumours) come from.

"They have obviously always been on different work regimes and both had different races last time.

"I don't know where it came from. I didn't see it if it was, maybe it happened, but I didn't see it."

Frankie Dettori admitted at Epsom on Thursday that he was on the lookout for a ride in the Derby.

When asked if he would consider the Italian, O'Brien said: "It would be very hard to get any better than Frankie.

"Everyone knows how good he is, he's a special man."

Connections of Arod warned that the improving colt will not run in the Derby if the ground went soft.

The Peter Chapple-Hyam-trained inmate made up lots of late ground at York on just his third career start to finish second in the Dante.

Jockey Jamie Spencer issued a slight advisory, however, in that Arod needs a sound surface to be fully effective.

The jockey said: "It looks like Arod is going to run in the Derby.

"He's a high-class horse and is lightly raced.

"He needs fast ground, so watch this space."

Those thoughts were echoed by Arod's owner, Sheikh Fahad, who said: "He needs good ground. Good to soft maybe, but not worse."

Michael Stoute, by contrast, would be unfazed if the ground was testing for Snow Sky.

The Khalid Abdullah-owned colt excelled in the Lingfield Derby Trial on 10 May and is already proven in demanding conditions.

The Freemason Lodge handler said: "He's entitled to go (for the Derby) after his Lingfield performance, we're hopeful.

"It’s still a long time away and Epsom drains very well.

"He won on soft ground at Salisbury and I'm not concerned about ground conditions."

Romsdal will work at Newmarket on Friday to determine whether or not he will be supplemented for the Derby.

Beaten just a nose by Orchestra in the Chester Vase, the Princess Haya of Jordan-owned colt could instead run at Royal Ascot.

Trainer John Gosden said: "He'll work in Newmarket and see what the owners want to do.

"He's in the King Edward at Royal Ascot, so it's up to them."

Stablemate Western Hymn, who defeated Snow Sky in April and subsequently won Sandown's Classic Trial, is very much on course for Epsom after he enjoyed a nice workout under William Buick.

He said: "Western Hymn enjoyed coming here today.

"He handled the hill, switched his legs very well and his head carriage is better."

Kingston Hill gained plenty of admiring glances from work-watchers as last season's Racing Post Trophy winner pulled a couple of lengths clear of two lead-horses in a 10-furlong stretch.

Roger Varian's colt finished eighth in the 2000 Guineas but has always been considered more suitable for the Derby.

Jockey Andrea Atzeni said: "He went really nicely. He travelled good and quickened up well.

"He handled the ground - it's pretty soft out there - but I was very pleased with him.

"We didn't go mad, we went a bit quicker down the hill as we wanted to see how he went round the bend.

"He pricked his ears when he got to the front, he always does that."

Andrew Balding worked Impulsive Moment, runner-up to Western Hymn at Sandown, in the hands of David Probert, who will have his first Derby ride.

The Kingsclere handler is set to have a second contender in Scotland, a well-beaten third in the Chester Vase but always held in some regard.