Historically, the allocation of weights for the Grand National marked a pivotal point for the prospects of trainers, jockeys and owners. It has cleared the path to big-race glory or produced a burden too heavy to overcome.
Unlike the other most prestigious steeplechase of the year, the Cheltenham Gold Cup, the Grand National is a handicap race. This means horses carry differing weights according to their previous form. The idea behind a handicap is to make for a more even race - the handicapper's ultimate (though in practice unfeasible) aim is for the horses to pass the winning post in a dead heat.
The Grand National is the only race in which the British Horseracing Authority’s Head of Handicapping Phil Smith can use his discretion to determine the weight each horse will carry.
The "best" horse in the race is given the top weight (about 11st 10lb) and the weights allotted to the other horses are set in relation to this. This means if the top-weighted horse drops out, the weights of the other competitors may alter but will not change in relation to each other.
Even if a horse is allotted a weight of 8st 12lbs, it must carry 10 stone as this is the required minimum. This means some horses will be carrying possibly a stone more than they should be (known as being out of the handicap) and this disadvantage should suggest they are likely to perform less well than their rivals. Many punters will automatically put a line through horses who are out of the handicap.
In allocating a weight to each horse, handicapper Phil Smith must take a variety of factors into account, including form - a horse's recent and previous performances - and the course: the so-called 'Aintree Factor' - does the horse like the track and is he proven over long trips?
The final field is determined by each contender's rating, with the highest-weighted horses given preference in a maximum field of 40.
No horse has won the National carrying more than 11st 7lb since Red Rum's record third victory, under 11st 8lb, in 1977. However, whilst in the 25 runnings between 1984 and 2009 only one winner (Hedgehunter in 2005) carried more than 11st, the win in 2010 of Don't Push It carrying 11st 5lb may herald a change in this trend.
Indeed, all of the last four winners have carried at least 11st, culminating in Neptune Collonges success under 11st 6lbs last season, and there is a widespread view, gaining popularity, that horses at the top of the handicap are no longer at such a big disadvantage, in part due to a new formula for handicapping the National which was devised in 2001 and has essentially compressed the handicap, decreasing the gap between the top-weighted and lowest-weighted horses and creating a more competitive race.
According to Phil Smith: "Looking back over the history of the race, we realised that the highly weighted horses had a moderate record, so we thought something needed to be done to try to not overburden the better horses."
Some 15 years ago, the Grand National field was still largely made up of horses out of the handicap and therefore carrying the minimum 10st weight - on the final racecard these could sometimes account for 70% of the field. But in the past few years, every horse has got into the handicap proper. In 1999, the lowest-rated horse in the race had an official rating of 110; in the 2011 renewal, the lowest-rated horse, Golden Kite, has a rating of 135. In other words, the quality of the field has increased by 25lbs in 11 years.
The result is that the top weighted horses will now have only a few pounds more than most of their rivals and will be giving no more than a stone and a half to any runner - a far cry from a century ago, when Manifesto, the 1897 and 1899 winner, gave 48lb to some horses in the 1900 race.
All of which means that shouldering a burden of 11st or more - previously considered insurmountable - is no longer the task it used to be. When Hedgehunter carried 11st 1lb in 2005, he was the first National winner to carry over 11st in 22 years. But 2009 winner, Mon Mome, carried 11st to win the race in a year in which the top four horses all carried 11st or more, whilst the 2010 winner - Don't Push It - carried 11st 5lb and the runner-up - Black Apalachi - carried 11st 6lb.
In a single, idiosyncratic race like the National, there will always be outsiders. But it is likely that Aintree has seen the last of winners such as Bobbyjo who, carrying 10st in 1999 and racing from 14lbs out of the handicap, streaked to victory by 10 lengths. In fact, the recent dramatic increase in the quality of horses taking part means Bobbyjo wouldn't have made the starting line in any of the past 10 runnings. According to Smith: "Weight is important but it's not the be all and end all, it's just the trainers who think it is."
Thus, whilst Red Rum remains the last horse to win the Grand National off top weight (and the first since the 1930s), it may not be long before that achievement is repeated – 2013 winner, Neptune Collonges, was the fifth top weight.
As sporting sights go, few can match the sheer excitement of 40 horses thundering towards the first fence at Aintree in the Grand National