Sepoy is a $12 chance with Paddy Power to become the second Australian, or expat, to win the Cup, up the gruelling 1200m course.
The favourite at $4 is Bated Breath, another who does not like heavy footing, who ran second in the King's Stand Stakes.
Australian-trained Ortensia, the unplaced favourite in the King's Stand, is an $11 chance.
Soul, a former Aussie owned by Darley and a close fourth in Black Caviar's Diamond Jubilee Stakes at Royal Ascot, is a $21 chance.
Plumptre said Sepoy faced the challenge of his glittering career to bow out a winner.
Sepoy hasn't raced since finishing near-last on the unfamiliar Tapeta surface in the Golden Shaheen at Meydan on March 31.
He has been given no favours under the weight scale, allotted 57kg as a Northern Hemisphere 4-year-old.
"At his best he is outstanding," Plumtre said. "I know he worked on Saturday morning and they must have been pleased otherwise he wouldn't be running.
"You look at a horse like Soul, who ran so well to Black Caviar. Sepoy could give Soul 3kg at weight-for-age and still beat him easily."
Plumptre said Sepoy rated superior to Starspangledbanner, who won the July Cup in 2010, and on-par with Choisir, who ran second in 2003.
Sepoy will be retired to Darley's Australian operation and will stand for a service fee of A$60,000.
Trainer Paul Messara is committed to running Ortensia. "She gets through it but she doesn't thrive.
"But quite a few of the fancied runners don't like it so the field could drop away a bit."
Ortensia will be ridden by the in-form William Buick, who will be instructed to get the mare into a comfortable rhythm to give her the best chance on the undulating 1200m course.
"I think the most important thing is balance and getting into a rhythm early," Messara said.
"I think we would be willing to sacrifice a position to get her balanced because that is the most important thing. Where we draw and how many starters there are will play a major role."
