Frankel is still set to head a star-studded cast on Champions Day at Ascot on Saturday (Sunday AEDT) as long as the ground is considered safe for the world's highest-rated racehorse.

The going at the Berkshire track on Friday afternoon eased from soft all round to soft on the straight course and soft, heavy places on the round course after three millimetres of rain.

Although a little more rain is expected before midnight, dry conditions are forecast for race day itself.

"We will look at it in the morning. It depends obviously what happens," Teddy Grimthorpe, racing manager to owner Khalid Abdullah, said.

"What I have always said is that as long as we are happy the ground is safe for Frankel that will be our call.

"We are going to walk it and the intention is to run if we can."

Frankel is unbeaten in 13 starts to date and the Champion Stakes over a mile and a quarter (2000m) is likely to be his final racecourse appearance.

Ascot is sold out in the anticipation of Frankel running and clerk of the course Chris Stickels is hoping the slight possibility of the Sir Henry Cecil-trained colt being withdrawn will not materialise.

"We desperately want Frankel to run," he told At The Races.

"We've had some rain this afternoon amounting to three millimetres and I've just changed the ground to straight course soft, round course, soft heavy in places.

"The rain should clear by midnight. It is drying back but the showers are on and off until then."

Cecil says "the adrenaline is going" as the curtain looks set to come down on Frankel's dazzling career although the trainer believes he is only now reaching his peak.

"The adrenaline is going, we've got him so far unbeaten and I'd like him to win at Ascot," Cecil told BBC Radio.

"He's getting easier, he used to be difficult, used to pull a lot. He's growing up, he's like me a late developer.

"He's a better horse, he's an improving horse.

"It's been a great honour (to train Frankel), slightly nerve wracking."

Whereas Frankel only ran for the first time over 10 furlongs in the Juddmonte International at York, Cirrus Des Aigles is as battle-hardened as they come - a fact which has not escaped Grimthorpe.

"Cirrus Des Aigles has proved himself after the last two or three years," he said.

"He's the defending champion and he came out at Longchamp and was very impressive in the Group Two.

"Certainly he's going to be a horse to be reckoned with."

PA AAP