Champion trainer Paul Nicholls is responsible for four of the 10 runners in the Champion Hurdle as he seeks to win this race for the first time.
Zarkandar, who lifted the Triumph Hurdle last year, is the pick of his quartet thanks to victory in the Betfair Hurdle at Newbury.
“Zarkandar won at Newbury and is in really good form. He’s four from four and you wouldn’t know how much improvement he might make,” said Nicholls.
“Rock On Ruby is a great price seeing how he ran against Binocular and Cheltenham will suit him better.
“I don’t think there’s much between the two, but maybe Zarkandar has more room for improvement.
“Celestial Halo didn’t run his race last time and was quiet for a few days afterwards. He doesn’t want the ground testing.
“Brampour isn’t a forlorn hope of picking up some crumbs and getting placed. He had some hard races before Christmas but is back to form now.”
Celestial Halo chased home Binocular in the Kingwell and has finished second and fourth in two previous Champion Hurdles.
His owner Andy Stewart would be chuffed with another top-four spot.
“If Celestial Halo is third or fourth we’ll be very happy,” he said.