But there are still five other Group 1s for thoroughbreds and lots of interesting angles to watch out for on Sunday.
The best horse in the world, based on Timeform ratings, is running at Longchamp on Sunday - but not in the Arc. Battaash, who runs in the Prix de l'Abbaye (16:30), had some doubters prior to his sizzling success in the Nunthorpe at York in August but won over the sceptics with an astonishing display of speed to win by three and three quarter lengths and lower Dayjur's course record set in 1990.
That sensational showing was not a one-off for Battaash. He is responsible for the top four performances over 5f in Britain in the last ten years. He also ran right up to his best when winning the Prix de l'Abbaye by four lengths at Chantilly in 2017.
He disappointed in the race last year – on the back of flopping in the Nunthorpe – but has a big class edge and is well clear on ratings.
French fancies for Gosden
John Gosden's fillies, spearheaded by Enable, have dominated this season and the trainer has a remarkable 47% strike-rate in Group 1s this year with such types. He had a strong hand to choose from in the Prix de l'Opera (15:55) but relies on Mehdaayih , who finished runner-up in the Group 1 Nassau Stakes last time, and the lightly raced Terebellum , who showed improved form to win a Group 2 at Deauville.
Mehdaayih had no luck in running in the Oaks at Epsom, but gained some compensation when landing a Group 2 at Saint-Cloud the following month and ran even better in defeat in the Nassau, shaping well having been asked to do a bit too much. She had no answer to Deirdre's late thrust but is a filly on the up and has a bigger performance in her.
Terebellum has yet to tackle Group 1 company but is worth a shot at it after improving plenty to win at Deauville and, with just three starts under her belt, should carry on progressing.
Leading the challenge for the home team is With You, who has run up to her best in defeat the last twice, going close in the Prix Rothschild and Prix Jean Romanet. She just about sets the standard but at a level the Gosden fillies have a good chance of surpassing.
Small but select French challenge in Foret
British trainers have won the last three runnings of the Prix de la Foret (17:05) and are heavily represented again, accounting for six of the 12 runners. Two Irish raiders and a German contender mean the French team is not strong numerically, but the presence of City Light ensures there is an excellent chance the prize will stay at home.
Stephane Wattel has largely campaigned City Light as a sprinter – and with a great deal of success. He won the sprint on All-Weather Championships Finals Day last year and finished a narrow runner-up in the Group 1 Diamond Jubilee Stakes at Royal Ascot later that season, showing form bordering on high-class.
He didn't need to be at his very best to score over seven furlongs at Longchamp last time but did so in ready style, showcasing an exciting turn of foot which will continue to stand him in very good stead.
Success for Japan on Arc day?
The Japanese have gone close to gaining a much-coveted Arc success on a number of occasions, most notably with El Condor Pasa (1999) and Orfevre (2012), who were both denied in agonising fashion. Three horses who are trained in Japan – Kiseki, Fierement and Blast Onepiece – will contest this year's Arc but it would be a surprise were any of them good enough to prevail against the likes of Enable and, coincidentally, Japan.
The best chance of a winner on Arc day with a Japanese connection rests on the shoulders of legendary jockey Yutaka Take, who has picked up the rides on Savarin in the Prix Marcel Boussac (13:15), Helter Skelter in the Prix Jean-Luc Lagardere (13:50), Soft Light in the Arc (15:05) , Commes in the Prix de l'Opera (15:55) and Jolie in the Prix de l'Abbaye (16:30).
Savarin is by Deep Impact – Japan's greatest Arc hope who was third past the post under Take in 2006 before being disqualified for testing positive for a prohibited substance.
Deep Impact had established himself as a top stallion before his death this year and in Savarin he has sired a talented filly who looks a leading contender for the Prix Marcel Boussac after winning the main trial, the Prix d'Aumale, in good style. The Jessica Harrington-trained Albigna, a disappointing sixth in the Moyglare last time, is the only challenger based outside of France.
In the Prix Jean-Luc Lagardere, Pinatubo's form will be put to the test as Armory – a seven-length second in the National Stakes – represents Aidan O'Brien, who is bidding for a ninth win in the race.