There was no-one more relieved to hear Criterion had been cleared to fly to Hong Kong than Robert Heathcote, trainer of his travelling companion Buffering.

Criterion was treated for mild colic on Sunday and there was a long wait on the tarmac a day later when the Australian Quarantine Service vet initially refused to clear him to travel from Melbourne.

He was eventually given the go-ahead and the pair arrived safely in Hong Kong in the early hours of Tuesday morning to get ready for the International meeting on Sunday week.

"I was very worried. It would have meant Buffering would have been on his own in the quarantine section at Sha Tin," Heathcote said.

"It also meant it would have cost $40,000 for three weeks in quarantine at Werribee when he gets back. With Criterion sharing it's only $20,000 and I was delighted when I heard he was on the plane."

Heathcote was even more reassured when he received a picture from his travelling foreperson Melanie Sharpe of the two horses nudging each other on the float from the airport in Hong Kong.

"The first thing Mel said was that she was amazed how bright and well and happy they were," he said.

"Buffering is a very sociable horse and it would have been terrible for him to be on his own."

Australian Derby winner Criterion will have his first start for new trainers David Hayes and Tom Dabernig in the Hong Kong Cup (2000m) while four-time Group One winner Buffering contests the Sprint (1200m).

Heathcote, who flies to Hong Kong on Wednesday, is keeping his expectations in check but knows he has a fit and sound horse.

"He has never disappointed us," he said.

"There are 21 of us going up there and I've said we should treat the trip as a celebration of all Buffering has done for his owners.

"It will be a party, and if he wins there will be an even bigger one."