These testing elements combined with the cauldron like atmosphere generated by the huge Aintree crowd have helped provide some huge upsets over the years.
We run through a few of the outsiders who did far more than just make up the numbers.
Foinavon (1967) – 100/1
Despite 51 years passing since his victory, Foinavon remains the ultimate proof that anything can happen in the National.
So slim were the outsider’s chances in the race that his owner John Kempton decided to go racing at Worcester instead of watching his horse win at Aintree.
With the field approaching the 23rd fence, the 100/1 shot had long tailed off but the ensuing chaos caused by the riderless Popham Dawn saw all those in behind him either fall or refuse.
Foinavon however was so far detached that his rider John Buckingham could take evasive action and become the only horse to successfully clear the fence first time
Despite 17 remounting they couldn’t chase down the outsider as he ran out the most unlikely of winners. The fence is now named in honour of him and will be the seventh taken by this year’s field.
Last Suspect (1985) – 50/1
Last Suspects lengthy price of 50/1 was born out of a track record that showed both eccentricity and ability in equal measure.
Yet as has happened so many times, The National fences galvanised a quirky type who, despite swishing his tail throughout the preliminaries and blundering badly at the third last, sprouted wings up the home straight to collar Mr Snugfit close to the line.
In winning he became the third and final winner trained by Captain Tim Forster and the first and only National winner in the colours of Anne, Duchess of Westminster made famous by the legendary Arkle.
Red Marauder (2001) – 33/1
A race run in biblical conditions; many joked that the Noah’s Ark could be seen coming into view as the 40 horses set off in one of the greatest Grand National slogs seen in the modern era.
The drama began at the Canal Turn when a mini-Foinavon incident saw loose horse Paddy’s Return block off a number of fancied runners.
Thereafter the field steadily eroded and eleven stamina sapping minutes later just four of the original 40 crossed the finishing line, led by the unfancied Red Marauder, piloted by 35 year-old Richard Guest.
His trainer and owner Norman Mason, for whom Guest doubled up as an assistant famously commented “Richard does everything”.
Mon Mome (2009) – 100/1
Venetia Williams’ then nine-year-old co-holds the record for the longest odds winner of the National, but unlike the aforementioned Foinavon, this win could not be attributed to a freak turn of events.
Under an assured ride from Grand National debutant Liam Treadwell, the supposed outsider put in a superb display to beat the previous year’s winner Comply or Die by a comfortable 12 lengths.
The race could have panned out very differently though as both horse and jockey survived a moment of panic during the first of two false starts.
Mon Mome had actually turned sideways and would have been left 20 lengths adrift if the starter had let them go first time round!
Auroras Encore (2013) – 66/1
The most recent odds upset saw the little known trainer and jockey combination of Sue Smith and Ryan Mania team up for victory.
Winning jockey Mania had previously retired from riding at the age of 21 due to a lack of rides but certainly justified his return to the saddle by guiding the former Scottish National runner up into the winner’s enclosure.
The race itself was notable in that all 40 runners made it to the Canal Turn without incident for the first time ever; while a record 32 of the 40 were still in contention heading into the second circuit.
With many more fancied rivals hogging the cameraman’s focus, Arouras Encore emerged from the pack to take up third spot after Valentine’s (the 25th fence) and then astonishingly took the lead with a superb jump at the last.
A strong finish saw him land the coveted prize by a facile looking nine lengths ahead of the more fancied Cappa Bleu and Teaforthree.