Two juveniles remain in the Nunthorpe entry, with the filly Ceiling Kitty, a 16-1 chance in pre-post betting, given a strong chance to upset her older rivals.
Ceiling Kitty, owned by Betfair founder Andrew Black, starred during Royal Ascot, with her victory over Hoyam in the Queen Mary Stakes.
Hoyam is also a Nunthorpe possibility and is rated a 33-1 chance.
Pearl Secret (6-1), who holds down the second line of betting behind Ortensia (5-1), is unbeaten in four starts. The colt is owned by Sheikh Fahad al Thani, a member of Qatar's royal family who came to prominence in Australian racing last year as the owner of Dunaden.
Messara returned to England late last week and he can't fault Ortensia's condition as she tries to go back-to-back overseas after her King George Stakes win at Goodwood.
"She looks a picture of health," Messara said. "She's certainly improved [since Goodwood] and she's probably as good as we could have her."
Messara received some bad news from home yesterday, when his multiple group placegetter Rekindled Alliance collapsed and died from a heart attack shortly after completing trackwork.
Rekindled Alliance finished fifth in the Australian Derby and was runner-up in the group two Phar Lap Stakes and Tulloch Stakes during the autumn.
He was also a valuable stud prospect being by Redoute's Choice out of Rekindled Affair and a brother to Rekindled Interest.
- AAP