Michael Stoute is well aware the Queen's filly Estimate faces the toughest test of her career in today's Gold Cup at Royal Ascot.

The four-year-old daughter of Monsun has won three of her six career starts and heads to the two-and-a-half-mile test as one of the least experienced members of the 18-runner field.

Nevertheless, she is a likely favourite having provided Her Majesty with a win at the meeting last year in the Queen's Vase and she also impressed on her seasonal reappearance.

Sent to the Sagaro Stakes over two miles at Ascot, Estimate ran out an impressive winner but she faces an extra half-mile and much sterner opposition this time.

Stoute is aiming for his second win in the prestigious race, having scored way back in 1978 with Shangamuzo.

"Her preparation has gone well," said Stoute.

"She enjoys Ascot, but this is much tougher than anything she has encountered before."

John Oxx's Saddler's Rock should possibly have a few more big-race wins on his CV than just the Doncaster and Goodwood Cups.

Not a horse seemingly blessed with a huge amount of luck, he was third in this race last year on unsuitably soft ground and things went badly wrong in the Dubai Gold Cup in March.

Smartly away under Declan McDonogh, his saddle soon slipped and his rider was unable to ride any kind of finish, doing well in the end to be as close as he was.

Oxx said: "He's been in good form. He got off to a great start in Dubai - he was in great shape there but then the saddle slipped when he was in the form of his life.

"It might not have been an ideal prep for him and he has to go there without a recent run, but hopefully it will work out and he'll run well.

"He's going well this year. He's been in better shape all round. Hopefully we'll have a good summer with him."

Oxx is pleased he decided not to run Saddler's Rock in the Saval Beg Stakes at Leopardstown earlier this month.

"The Saval Beg used to be a better trial for the Gold Cup, but it's just 13 days beforehand now and is a bit too close," he said.

"It's fine if you don't get too hard a race as a prep run, but it would have been a tough enough race close to the Gold Cup so we're happy we missed it."

Francois Doumen remains better known in Britain for his handling of top-class jumpers such as The Fellow and Baracouda, but in recent years has had plenty of success with his Flat runners.

He saddles Group Two winner Top Trip, who was beaten just a nose in the Yorkshire Cup by Glen's Diamond, with his trainer expecting enough improvement from York to make him competitive.

Doumen, who twice ran Kasbah Bliss in the Gold Cup, said: "I think the (soft) ground was the reason he ran so cool during the race at York. It shows how good he is that he was still nearly able to win.

"He should run a proper race, he has improved a lot since York, his rating has gone up a long way anyway.

"I think he will stay, he's so relaxed he should stay forever."