The Ralph Beckett-trained Westover will lock horns with Emily Upjohn and Mishriff who have both stood their ground for the showpiece Group 1.
Westover completed an impressive demolition job in the Irish Derby last month, but is unlikely to have things all his own way under Colin Keane, with John and Thady Gosden firing a formidable two-pronged assault.
Emily Upjohn was due to contest last weekend's Irish Oaks following her narrow defeat in the Oaks at Epsom, but travel problems meant she missed out on a trip to the Curragh.
As a result, Frankie Dettori's mount joins her illustrious stablemate Mishriff, who was second to Adayar in last year's King George and proved he is as good as ever when touched off by Vadeni in the Eclipse three weeks ago.
James Doyle partners Mishriff for the first time, replacing owner Prince Faisal's former retained rider David Egan.
German raider Torquator Tasso, a shock winner of last year's Prix de l'Arc de Triomphe, adds international spice to the six-strong field.
Aidan O'Brien, who has previously struck gold in the mile-and-a-half contest with Galileo (2001), Dylan Thomas (2007), Duke Of Marmalade (2008) and Highland Reel (2016), this year relies upon Broome, who won the Hardwicke Stakes over the course and distance on his latest appearance.
The small but select field is completed by William Muir and Chris Grassick's stable star Pyledriver, who found Hukum too strong when defending his crown in Epsom's Coronation Cup last month.
With his regular rider Martin Dwyer sidelined by injury, and Dettori, who has been on the board the last twice unavailable, PJ McDonald takes over in the saddle.
Beckett was in confident mood about Westover's chances ahead of the race.
"He's trained well since, we've been happy with him and he looks like he's ready to go," Beckett told TalkSPORT2.
"Races like this are what we all do it for, days like Saturday, they don't come around too often so you've got to make the most of them.
"Juddmonte have an agreement with Colin Keane to ride their horses when he's available. This is just an extension of that.
"We don't have a stable jockey, we have three jockeys who ride for us regularly but if an owner wants someone else that is their prerogative and all concerned understand that.
"Colin obviously knows the horse now and in that sense it is pretty straightforward.
"It was great for Rob to win the Falmouth (on Prosperous Voyage), he's been coming here once or twice a week for the last three years and that has been a very happy arrangement and we've had plenty of luck, that was a second Group One inside nine months."