|Crabbie's Grand National 2016|
|Venue: Aintree Date: Saturday, 9 April, 17:15 BST|
|BBC coverage: Commentary and updates on Radio 5 live; live text commentary, pinstickers' guide, sweepstake kit on BBC Sport website|
Last year's winner Many Clouds will bid to emulate Red Rum by winning back-to-back runnings as 39 horses line up for the Grand National on Saturday.
Jockey Leighton Aspell, also successful in 2014 on Pineau De Re, is seeking a historic third consecutive victory in the famous race over 30 fences.
The field was reduced on Saturday when O'Faolains Boy, trained by Rebecca Curtis, was found to be lame.
Coverage of the £1m race is expected to be followed by 600m people worldwide.
Bookmakers say more than £150m will be wagered on the race.
Two-time winner Ruby Walsh, who was set to ride Sir Des Champs, was ruled out with a fractured wrist after falling twice on Friday.
The Aintree showpiece - run over nearly four and a half miles - has been put back an hour to 17:15 BST, avoiding a clash with the afternoon's football fixtures, in an effort to increase audience figures.
|8-1 Many Clouds; 12-1 The Last Samuri; 14-1 Shutthefrontdoor 16-1 Holywell, Silviniaco Conti, The Druids Nephew, Saint Are, Gallant Oscar, 20-1 Gooonyella; Morning Assembly 25-1 Bar(Approximate prices as of 11:30 BST, Saturday 9 April)|
History in the making?
Contenders have to negotiate obstacles such as Becher's Brook and The Chair, and no horse has won back-to-back runnings since triple-winner Red Rum in the 1970s.
But Aspell believes Many Clouds, rated 8-1 favourite on Friday, can defy top weight for trainer Oliver Sherwood.
"I think he's the worthy favourite. I would choose Many Clouds for his experience and class. He's possibly still improving," said Aspell, 39.
However, the jockey did concede that Silviniaco Conti, a seven-time winner of Grade One races at the highest level, had the capability to "make a mockery" of his 16-1 odds.
|Red Rum in the Grand National|
Who are the other leading contenders?
Punters will keep a keen eye on the weather, with 7mm of rain overnight changing the going at the track to Soft, Good to Soft in places.
Any rain would be considered a plus for last year's Midlands National winner Goonyella, while the Jonjo O'Neill pair of Holywell and Shutthefrontdoor would prefer drier conditions.
Other leading contenders include The Last Samuri for trainer Kim Bailey, who triumphed 26 years ago with Mr Frisk.
Sir Des Champs, the 2013 Cheltenham Gold Cup runner-up trained by Willie Mullins, saw his 40-1 odds halve after Walsh was confirmed as jockey.
However, Nina Carberry will deputise for Walsh following his injury.
A National Velvet moment?
Along with Carberry, Ruby's sister Katie is seeking to become the first female rider to win the National.
Katie, who achieved a best-placed finish of third in 2012 on Seabass, rides outsider Ballycasey for Mullins having been called up for the ride on Wednesday night.
As a child she watched the movie National Velvet, in which Elizabeth Taylor plays a young woman who rides the Grand National winner, but does not overplay her gender.
"I don't see myself as a female jockey. I'm just a jockey," said the 32-year-old Irish amateur.
"Loads of people say that if I win the National, I would be the first female to do so. I don't see it like that. I just think it would be great to win."
Are there safety concerns?
The National is famed as a unique test for horse and rider, but draws criticism from opponents, including animal welfare groups.
Officials believe modifications to the fences, and other alterations, introduced three years ago have helped improve safety.
Since the changes, there have been no fatal injuries to horses in the National itself, but there were three fatalities over the National fences on the first two days of this year's Aintree meeting.
In Thursday's Fox Hunters' Chase, Clonbanan Lad and Marasonnien did not fall, but were pulled up by their jockeys and later collapsed.
On Friday, Gullinbursti and Minella Reception were put down after a fall at Becher's Brook in the Grade Three Topham Chase.