Owner Andy Stewart feels ante-post favourite My Will is "far too short" a price for tomorrow's John Smith's Grand National at Aintree.

The nine-year-old has been all the rage for the world's most famous steeplechase since he ran a mighty race to finish fifth in the Cheltenham Gold Cup last month, meaning he is 8lb well-in according to the official handicapper.

News that dual Grand National-winning jockey Ruby Walsh will be in the saddle has only seen his price contract even further and he is trading at a general 7-1.

"It's great Ruby chose to ride him and it's a major plus for a horse who sometimes makes the occasional mistake," said Stewart.

"Having a jockey with that experience round Aintree and who has also ridden the horse beforehand is important.

"I think the price the bookmakers have got him is far too short and he should basically be that price to get round.

"But he's never been better so there will be no excuses and Paul Nicholls is feeling very bullish," he said.

Barking-based bookmakers Coral believe the huge punter and public popularity of Walsh could see My Will start the most heavily-backed favourite in the history of the race.

Spokesman Simon Clare said: "Ruby Walsh will be the name on every punter's lips this weekend and his huge public support could see My Will's odds start 5-1 or even shorter.

"Ruby has a brilliant record at Aintree, has just battered the bookies with his stunning seven winners at the Cheltenham Festival, and is riding the National favourite trained by the Champion trainer.

"With that profile it is possible that My Will will start the most heavily-backed favourite in the history of the race."

In contrast, Tony McCoy has never won the National and he was confirmed as the rider of Butler's Cabin after the 13-times champion jockey had been deliberating all week which one of four horses he would ride for his boss JP McManus.

After leaving the decision as late as possible, he has sided with Butler's Cabin, whom he rode in the race 12 months ago before the pair parted company at Becher's Brook on the second circuit when still travelling strongly.

"Tony has decided to go with Butler's Cabin and all four horses of ours will run," said McManus' racing manager Frank Berry.

"Robert Thornton will ride L'Ami, Noel Fehily rides Can't Buy Time and Mark Walsh rides Reveillez."

Dominic Elsworth has been replaced by Wayne Hutchinson for the ride on leading fancy Darkness, having not ridden in a race since taking a crashing fall at Towcester a week ago.