Italian riding great Frankie Dettori got a surprise chance at partnering a fourth Prix de l\'Arc de Triomphe winner on Wednesday when he was called up to ride Irish champion Camelot. The 41-year-old - who won the last of his three Arcs in 2002 on the shock winner 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. Dettori, who lost what he thought was his last chance of a ride when English mare Snow Fairy was withdrawn with a leg injury last Friday, was ecstatic to have landed the ride on Camelot, who has won the Epsom and Irish Derbies and the English 2000 Guineas this season. \"It\'s an honour for me to ride the horse,\" said Dettori. \"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 only 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 finishing second behind 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. \"In the Leger he was ridden to stay and it was a stop and start kind of pace early on and I still think he quickened really well in the end. He\'s better judged on his two previous wins which were pretty impressive.\"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, the four-year-old colt is 5/2 with Camelot generally available at 3/1. Orfevre, bidding to give Japan their first win in the race after 12 previous runners failed to over the past 32 years, had his final serious gallop on Wednesday, watched by a large group of Japanese media, and pleased his trainer Yasutoshi Ikee. \"He is improving every day and has been since he won the Prix Foy,\" said Ikee afterwards. \"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 with only a fear of the rain dampening his enthusiasm. \"She is in greast shape, she has really come on in the past year winning two Group Ones, in England (the Yorkshire Oaks in August) and then the Vermeille at Longchamp (in September),\" the 68-year-old two-time Arc winning handler told AFP. \"Her qualities is 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.\" De Royer Dupre said he was mulling over whether to supplement Bayrir for 100,000 euros on Thursday. \"He is a charming and discreet horse, with a great temperament, he has gradually progressed and won a Group One in the United States this season,\" he told AFP. \"Three year olds have a good record in the Arc but it is always difficult to say how the classic generation will fare against the older more experienced horses.\" De Royer Dupre, though, wasn\'t so enthusiastic about running his French Derby winner from last year Reliable Man but admitted it wasn\'t solely up to him. \"I don\'t really want him to have a hard race I would prefer he went for a Group One I have in mind for him in Canada, but the owners may have other ideas.\"