Rated the second-highest horse in the world this year, Rebel's Romance  will chase a fifth Group 1 having eclipsed a star-studded field containing 10 individual Group 1 winners in the G1 Dubai Sheema Classic (2410m) at Meydan Racecourse on 30 March.

Trained by Charlie Appleby, Rebel's Romance is a clear benchmark according to Purton, who is chasing a third win in Hong Kong's final Group 1 of the season after the Australian's victories on Exultant in 2019 and 2020.

With an international mark of 106, Massive Sovereign meets 123-rater Rebel's Romance (126lb) at equal weights, while Purton is also concerned at the prospect of further rain.

"The forecast is a worry, really, and he (Massive Sovereign ) is a long way out of it on the handicap and the horse (Rebel's Romance) that's come to Hong Kong is a serious horse - if he runs four lengths off his best on ratings, he's still got the field covered," Purton said.

"It's a big challenge. We're just hoping to get him onto a dry track and assess him a little bit more after last start but the weather doesn't look like it's going to play ball, so we'll have to deal with it."

A brilliant winner of the BMW Hong Kong Derby in record time at only his second Hong Kong start, Massive Sovereign floundered on yielding ground when beaten more than eight lengths by Romantic Warrior in the G1 FWD QEII Cup (2000m) on 28 April.

Hong Kong champion trainer in 2012/13, Yip believes Massive Sovereign can atone for his last-start performance as long as the conditions are suitable.

"He's in very good form and hopefully the rain stays away for him. If the ground is rated good, I think he will show everyone something," Yip said. "We are very happy. He's eating well and every day he is working perfectly.

"I think (Rebel's Romance) is very strong and his form looks like it will be hard to beat him. But, (of) all the Hong Kong horses I'm not sure.

"It will be a very interesting race. We don't know the ground of course, but I think Massive Sovereign will be able to run a big race and finish very well."

The Standard Chartered Champions & Chater Cup will feature four Irish-bred horses – Rebel's Romance, Five G Patch, Russian Emperor and Massive Sovereign – Straight Arron and Senor Toba from Australia, La City Blanche from Argentina and Chile-bred Moments In Time.

Moments In Time will be ridden by Lyle Hewitson, who hopes the dual Hong Kong winner can surprise after a last-start fourth in the G3 Queen Mother Memorial Cup Handicap (2400m) on 5 May, when he led and was caught late.

"Of course, at the weights, he's far out of it but at his last run - even though he had the bottom weight (115lb) - he was doing far too much for too long and the fact he could stay on so well was quite impressive," Hewitson said.

"I think over this trip if he has a genuine lead - but without competition the whole way - he could be quite dangerous. I know it's going to be a hard task to win but I wouldn't be surprised if he raised his game and could earn some good prizemoney.

"His gallop the other day on the grass, he was very fluent in his action. His ears were pricked and he never put in a wrong step, so I think he could handle it (potentially rain-affected conditions). He's not a big horse, either, so he gets over the top of it comfortably and I don't think it's an issue, so I think he's one who'll go under the radar a little bit."

Sha Tin's 10-race card on Sunday (26 May) starts at 12.45pm with the Pakistan Star Plate (1200m) for Griffins.