The John Smith's Grand National is undoubtedly the world's most famous race and with record prize money of £975,000, it's also easily Britain’s richest Jumps race.
The race is over a gruelling four miles and four furlongs (7200 metres) and due off at 4.15pm (BST) on Saturday, and will take around 10 minutes to run.
Cheltenham Gold Cup hero Synchronised heads a maximum field of 40, as he bids to become the first horse since Golden Miller in 1934 to win the Gold Cup and Grand National in the same season. He is ridden by the champion jockey Tony McCoy, who won the great race in 2010 on Don't Push It.
He will face strong opposition from last year's winner Ballabriggs, trained by Donald McCain. Ballabriggs will attempt to be the first since the legendary Red Rum, trained by McCain's father Ginger, to land back-to-back victories in the world's greatest steeplechase some 36 years ago.
On His Own, the mount of Ruby Walsh, heads Willie Mullins' team while the Irish jockey's sister Katie will be aboard Seabass for their father, Ted Walsh.
Nina Carberry, who is also bidding to become the first female rider to win the race, will be aboard Organisedconfusion for her uncle, Arthur Moore.
Among the other major contenders are Giles Cross, West End Rocker, Junior, Cappa Bleu, Chicago Grey and Killyglen.
More than £300million is expected to be bet on the Grand National and one of the best-backed horses throughout the industry this week since the rains came has been West End Rocker, who is now as low as 11-1 from 20-1 earlier this week.
However, Synchronised is the most popular choice to land the money as he ticks all the right boxes - he's got stamina in abundance, had the quality to win a Gold Cup and has the assistance of the world's best Jumps jockey.
The chief supporting race is the Grade 1 John Smith's Aintree Hurdle, in which Oscar Whisky and Thousand Stars, who fought out the finish last year, do battle again over two and a half miles (4000m) at 2.50pm.
The Nicky Henderson-trained Oscar Whisky got the verdict by a neck over Willie Mullins' runner when just holding on for victory in the Grade 1 on Merseyside last April.
Thousand Stars gained some revenge of sorts in the Ladbrokes World Hurdle at the Cheltenham Festival when finishing one place and a length and a half in front of his old rival when fourth to Big Buck's.
However, these two are unlikely to have things all their own way as the field of six horses declared includes Champion Hurdle winner Rock On Ruby.
Noel Fehily, who partnered the Paul Nicholls-trained seven-year-old at Cheltenham, will again be in the saddle. Nicholls' stable jockey Ruby Walsh will be aboard Zarkandar, who was fifth in the Champion.