Triple classic winner Camelot's chances of running in and winning Europe's most prestigious horse race, the Prix de l'Arc de Triomphe on Sunday, have increased with the seemingly inevitable withdrawal of last year's winner Danedream.

With Danedream incarcerated at the Cologne racetrack stables, which has been closed down for three months after a horse was diagnosed with the highly contagious equine infection of the blood, and also the withdrawal of last year's third Snow Fairy, the pressure will mount on trainer Aidan O'Brien to commit Camelot to the fray.

O'Brien - who has won the great race just once with Dylan Thomas in 2007 - has yet to make up his mind whether to run his stable star, who has collected the English 2000 Guineas and Epsom and Irish Derbies this season.

However, he had a really hard race in the English St Leger last month as he failed to emulate the great Nijinsky's Triple Crown feat achieved in 1972 in finishing second behind longshot Enke.

The main problem for the 42-year-old Irishman is not so much the race itself and whether Camelot has recovered from his St Leger exertions but who he can get to ride the horse as his son Joseph is unable to. Joseph had ridden him in all his races this term but because of his 6ft height he has a constant battle with the weight.

The list of jockey options is not a lengthy one as O'Brien's favoured first alternative Ryan Moore is taken as Sir Michael Stoute is running Moon while Belgian ace Christophe Soumillon is claimed by Japanese favourite Orfevre's connections.

While a tough race in the St Leger can prove costly in the Arc - aside from the difference in distance with the Leger being 1¾ miles to the Arc's 1½ miles - as Nijinsky found to his cost when finishing second at Longchamp - there are also other horses that have thrived on the closeness of the races.

Alleged - trained like Nijinsky by the late Vincent O'Brien who is no relation to Aidan but trained at the same stables in Tipperary -finished second in the 1977 St Leger before going on to win at Longchamp and then returned to France a year later to win a second Arc.

He is the last horse to win successive Arcs and with Danedream's double bid looking all but over through no fault of her own, O'Brien's chances of declaring later this week that Camelot will indeed take part can only have got stronger - provided of course he can find a knight in shining armour for him.