The legendary status of mighty mares Winx and Black Caviar has only been enhanced following the unexpected defeats of three of world racing's best racehorses.

English super mare Enable was beaten chasing her 13th successive win in the Prix de l'Arc de

Triomphe at Longchamp earlier this month while the winning sequences of Hong Kong's Beauty Generation and Europe's best stayer Stradivarius ended at 10 after their shock losses Sunday.

The champion trio's aura of invincibility has been shattered, demonstrating just how difficult it is to continue winning over an extended period at racing's top level as Winx did for the final 33 races of her career while Black Caviar was unbeaten in all 25 starts.

Beauty Generation suffered his first loss in 18 months when he ran third to Rise High in the Group 2 Sha Tin Trophy.

Hong Kong racing fans were left stunned as Beauty Generation was run down as a long odds-on favourite. The handicap conditions of the race didn't favour the champ as he conceded plenty of weight to his rivals.

But Beauty Generation wasn't able to assume his customary front-running role and this ultimately led to his defeat. "He's a better horse when he's left to run along. When he's in the box seat like that he just doesn't show the same turn of foot," trainer John Moore told Hong Kong media.

"I would've rather drawn a wider gate, then he could come across and been where he wants to. Getting the gate two was probably the negative. I'm not worried. It's one of those things.''

Stradivarius seemed set to end another perfect year when he loomed up alongside Kew Gardens halfway down the straight in the British Champions Long Distance Cup at Ascot.

But Kew Gardens, trained by Aidan O'Brien, was in for the fight and edged out Stradivarius after a thrilling duel to the finish.

John Gosden, trainer of Stradivarius, said the soft track conditions brought his stayer undone, just as it did to his stablemate, Enable in the Arc.

"It was very bold and sporting of Mr (Bjorn) Nielsen (owner) to run Stradivarius but he just found the ground too soft,'' Gosden said.

"He did well to win it last year as they went no pace. This year he found it too much of a slog in the ground. He has run a wonderful race. Take nothing away from the winner, we headed him and he's come back.''