If Willie Mullins' charge can come home in front in the four-and-a-half-mile marathon, he will be the first dual winner since the Ginger McCain-trained Red Rum lifted the prize in 1973 and '74.
The 10-year-old was last seen finishing second in the totesport Cheltenham Gold Cup and he will have to defy joint top-weight of 11st 12lb.
Michael Meagher, racing manager to owner Trevor Hemmings, said: "Willie is very happy with him but 4-1 is a ridiculous price."
Hemmings will have a second string to his bow in the shape of Juveigneur, who is trained by Nicky Henderson.
The nine-year-old finished second in the William Hill Trophy Chase at Cheltenham on his last start and he will have the benefit of 1996-winning rider Mick Fitzgerald in the plate.
"I think Mick rides Juveigneur," Meagher added. "He ran a great race at Cheltenham.
"He's been round there before in the Topham and Mick said he was just adequate but they schooled him last week he jumped away great so they are happy enough and they are going there positive enough with him.
"He was second in the Betfred and he'd have a squeak."
Juveigneur is a 25-1 shot with both Coral and Ladbrokes.
The latter firm report some significant backing for the Sue Smith-trained Ross Comm and have shortened him to 20-1 from 25s despite the horse still not being guaranteed a run.
"If he gets in, he'll give them all a run," said the trainer's husband, Harvey Smith.
Haut De Gamme is another to have been well-backed with Ladbrokes and he is now 33-1 from 40s to give trainer Ferdy Murphy a first National win.
The 11-year-old, runner-up in the Topham and fifth in the Becher Chase over the daunting National fences last year, is the choice of stable jockey Keith Mercer and David Parry, syndicate manager for owners David Parry Racing, is hoping for a big run.
"We've kept him to hurdles to protect his mark this season and it looks like it has all gone to plan," he said.
"He has jumped round Aintree twice with some success and he'll be a real live contender come Saturday, especially if it keeps raining."
Murphy also runs last year's Scottish National runner Joes Edge and although Mercer has chosen to ride his stablemate, Murphy believes the 20-1 shot is in with a shout.
"We're very happy with Joes Edge, he ran a blinder in the Gold Cup, we finished just in front of Cornish Rebel and we are nearly a stone better off with him on Saturday," said the Middleham handler.
Heros Collonges, one of seven intended runners from the Paul Nicholls yard, will sporting new colours on Saturday after being sold for an undisclosed fee by John Hales.
The 11-year-old will race in the colours of Haydock-based company Merchant Rentals plc as he tries to improve on last year's eighth place.
Four horses Risk Accessor, Direct Access, Colnel Rayburn and Iris Royal - are currently on 10st 6lb and three of the four will be guaranteed a run after National handicapper Phil Smith reassesses the race today.
Only 12 entries were taken out, with Henderson as expected removing both Fondmort and Calling Brave.
Celtic Son, Seebald, Joly Bey, Europa, Another Rum, Kymandjen, Marcus du Berlais, Coljon, Bounce Back and No Retreat were the other withdrawals.
John Smith's Grand National betting:
Coral: 4-1 Hedgehunter, 5-1 Clan Royal, 12-1 Dun Doire, Numbersixvalverde, Innox, 14-1 Sir Rembrandt, 16-1 Cornish Rebel, Jack High, 20-1 Garvivonnian, Lord Of Illusion, Ross Comm, Royal Auclair, Silver Birch, 25-1 Direct Access, Haut De Gamme, Joes Edge, Juveigneur, Therealbandit, 33-1 bar.
Ladbrokes: 4-1 Hedgehunter, 5-1 Clan Royal, 10-1 Numbersixvalverde, 14-1 Dun Doire, Innox, Jack High, 16-1 Sir Rembrandt, 20-1 Cornish Rebel, Garvivonnian, Joes Edge, Ross Comm, 25-1 Colnel Rayburn, Direct Access, Juveigneur, Lord Of Illusion, Royal Auclair, Silver Birch, 33-1 bar.
Cashmans 5-1 Hedgehunter, Clan Royal; 10-1 Num'sixvalverde; 12-1 Innox; 14-1 Jack High; 16-1 Royal Auclair, Sir Rembrandt, Lord Of Illusion, Cornish Rebel, Garvivonnian; 20-1 Silver Birch, Le Duc, Joes Edge, Ross Comm.