Junior will attempt to drag the stamina out of the opposition when he aims to justify a late entry for the King George VI Chase at Kempton on Boxing Day.

Owners Middleham Park Racing stumped up STG10,000 ($A15,770) to add the David Pipe-trained nine-year-old to the field and believe they can a get run for their money.

A rare winner at both the Cheltenham Festival and Royal Ascot, Junior showed his well-being with victory in the Rehearsal Chase at Newcastle, his first run since he fell at the second fence in the Grand National at Aintree in April.

"I don't think it's a classic King George - no Kauto Star, no Denman - and I fancy our chances," said Nick Bradley, spokesman for owners Middleham Park Racing.

"There is no obvious front-runner in the race, other than ourselves.

"Newcastle was a confidence-building run. He wasn't quite 100 per cent fully tuned up.

"The plan was to go for the Rowland Meyrick (at Wetherby) and try to build-up for his confidence for the end of the season.

"Then myself and Tim (Palin, Middleham racing manager) were looking at the King George and we couldn't think of any three-mile (4800m) horses in there.

"When you are told the ground is going to be heavy or soft, personally I would have doubts about a few of them staying."

Long Run is the dominant King George favourite and is as short as 7-4 with Junior a 20-1 chance.

The recent storms in Britain have put paid to Thursday's Well Grand National at Chepstow which has been rescheduled to January 5.