Italian riding great Frankie Dettori has received a surprise call-up to ride Irish champion Camelot in the Prix de l'Arc de Triomphe on Sunday.

The 41-year-old, who is retained by Godolphin and won the last of his three Arcs in 2002 on Marienbard, got the rare ride on an Aidan O'Brien trained-horse because the Irishman's son Joseph cannot ride the weight of 8 stone 11 pounds (56kg).

Dettori, who lost what he thought was his last chance of a ride when English mare Snow Fairy was withdrawn with a leg injury last Friday, was ecstatic to have landed the ride on Camelot, who has won the Epsom and Irish Derbys and the English 2000 Guineas this season.

"It's an honour for me to ride the horse," Dettori said.

"Let's hope he's in tip top shape, he's had a pretty long season now but if the Camelot we know turns up he should have a very good chance."

Camelot, who would be O'Brien's second winner of Europe's most prestigious race, was given the green light to run after he impressed in a gallop with fellow entrant St Nicholas Abbey on Wednesday.

There had been doubts as to whether he would run after he failed to seal the 'Triple Crown' when second to long shot Enke in the English St Leger last month.

"I think you want to judge the horse more on the Guineas and Derby runs," said Dettori, whose employers Goldolphin haven't got a runner in this year's renewal.

Despite the news of Dettori being given the ride it was not enough to dislodge 2011 Japanese Horse of the Year Orfevre from the top of the betting.

Bidding to give Japan their first win in the race after 12 previous runners failed over the past 32 years, Orfevre had his final serious gallop on Wednesday and pleased his trainer Yasutoshi Ikee.

"He is improving every day and has been since he won the Prix Foy," Ikee said.

"As for his habit of losing interest and dropping back (he lost 25 lengths in one race in Japan before recovering to win) I don't mind that so much, so long as he finds his rhythm," added Ikee, who will run Aventino as a pacemaker.

France's most fancied contender Shareta, second last year when a pacemaker, didn't work on the gallops on Wednesday but trainer Alain de Royer Dupre said he was excited about her prospects.

"She is in great shape, she has really come on in the past year winning two Group Ones," the 68-year-old two-time Arc winning handler told AFP.

"Her qualities are that she is bigger physically than most horses, and is very imposing.

"She is a late developer especially with regard to her acceleration and that is especially important at the start as she uses it to get well-placed, which means she gets to avoid the traffic problems."