You could not find a cooler head for a Royal Ascot mission of quite enormous importance than John Velazquez.

Animal Kingdom heads for the Queen Anne Stakes as perhaps the greatest American-trained horse to run in Britain, certainly as good as any since another Kentucky Derby winner, Reigh Count, failed in Berkshire in 1929.

It will be the stunning chestnut's final start, and victory will make him a considerably more valuable stallion commodity when he starts his stud career at Arrowfield in Australia.

A son of the Brazilian-bred Leroidesanimaux, Animal Kingdom has a fascinatingly mixed pedigree including German bloodlines and is of such interest that Sheikh Mohammed's Darley Stud has also purchased a substantial interest in him.

As a winner of the 2011 Derby, as well as second in the Preakness and Breeders' Cup Mile during a truncated career, he has already achieved the remarkable by switching to a third surface, Tapeta, with an impressive victory in the Dubai World Cup.

'Johnny V' takes over again after a 16-month hiatus and flew across to Ascot late last month simply to ride Animal Kingdom in a racecourse gallop.

Velazquez, who has sat on such horses as Da Hoss, Lemon Drop Kid, Kitten's Joy, Rags to Riches, Uncle Mo and Animal Kingdom, was asked if he was special.

"Definitely - by far," he said. "They don't come that often like that.

"For a horse to come and run on different surfaces and have done what he has done, there are aren't that many horses.

"The special horses give you a great feel when you're on top of them. You hope they can stay that way by the day of the race."

American-based jockeys have been scoffed at by the traditionalists in the past when they struggled to transfer their clinical timing on the level dirt ovals to the varied British courses.

However, this is no Johnny-come-lately, as the 42-year-old rode half a dozen Godolphin horses at the 2000 Royal meeting when Frankie Dettori was injured.

He was then back nine years later to win several two-year-old races for Wesley Ward and even slipped in another brief visit in 2011.

Speaking slightly accented English, no doubt reduced by spending more than half his life in America, the likeable Puerto Rican is unfazed by a return.

"It's great, it's very exciting to be here again," he said.

"Obviously they are running the opposite way, which is very different for us, and you've got to get adjusted to it.

"I've ridden it a couple of times now but to get adjusted right away, I was a little bit in shock, but you walk the course and you watch the races."