The Noel Meade-trained five-year-old is as short as 3-1 from 9-2 with Hills, while Coral are 7-2 from 5-1 and Ladbrokes 4-1 from 5-1.
The Stan James Christmas Hurdle triumph - on Paul Carberry’s first ride at the Sunbury course - looked unlikely at the home turn as Rooster Booster, who had stolen a march on his rivals at the start, still held an advantage of over 15 lengths.
Only between the last two flights did Carberry begin to eat into the leader’s advantage significantly, but on the run-in Harchibald (8-11) proved much too strong and looked good value for his winning margin of a length and a half.
It was a further 20 lengths back to the third home, Perouse.
Meade, who was at Leopardstown, indicated that the Irish Champion Hurdle at the track in February was the next target.
He was represented at Kempton by partner Gillian O’Brien, who said: “Wow! It’s always a hard one to judge when you have to go after a good horse with a big lead, but Paul said turning in Harchibald was absolutely cantering and he was in no doubt he would catch him.
“The horse seems to be growing in confidence all the time and he jumped great today. It’s roll on Cheltenham.”
Asked whether she was in any doubt of Harchibald’s ability to come up the hill at Prestbury Park, which he appeared to fail to do when beaten in last season’s County Hurdle, she added: “We have no fears about that. Paul said the further they went the better he travelled and I think he’s a stronger horse this season.”
Carberry observed: “I let Rooster Booster pull me for as long as possible but I was always going to get him. He really jumped and I never hit him once.”
Connections of Rooster Booster took this defeat firmly on the chin and owner Terry Warner is looking forward to his veteran attempting to regain his crown next March.
Warner said: “The crowd really got behind him today and for a while I thought Richard Johnson had nicked it under a very good ride. In the Champion it will be back to our old hold-up tactics.”
Philip Hobbs has stated his keenness to let Rooster Booster try to better his short-head second to Geos in the Tote Gold Trophy at Newbury, and of that, Warner said: “We might attempt it. The other race before the Festival would be the Agfa Hurdle at Sandown.”