The Grand National is billed as the world's greatest steeplechase. The race has been staged at Aintree racecourse in various forms since 1839. It is run over a distance of almost four and a half stamina-sapping miles with a total of 30 fences to be negotiated by 40 runners before a punishing slog up the home straight over the finish line and into the history books. The race is not only a marvelous spectacle but also a massive revenue generator through betting, sponsorship, TV broadcasting rights and the course operators.

The race also courts controversy. Only 37 percent of runners have actually completed the race in the last 10 years. In the last 50 years, 36 horses have either been killed during the race or sustained injuries necessitating euthanasia subsequently. Clearly, jumping substantial fences at speed surrounded by a large group of other runners is a recipe for accidents and tragically horses are often killed and injured during the jumps racing season; but what makes the Grand National so very deadly?

Could the problem lie with the famous fences themselves? The Grand National fences are certainly unique. Their construction is different from those found at other UK racecourses. They are bigger both in height and spread and many have ditches on either side which are deeper and wider than horses are accustomed to negotiating. Following public concern and pressure from animal rights groups, fence heights have been reduced in recent years and the drops made less severe and punishing. In 2009, run-outs were introduced to try to remove the hazard of loose horses from the course. For this year's race, the organisers have announced that all fences will have a different, softer core structure.

Statistically, falls are spread fairly evenly around the course although the 'feature' obstacles do have a slightly higher fatality rate. Could this be because the obstacles are so different from the norm?

Becher's Brook: A four foot ten inch fence and ditch positioned on a diagonal with a drop on the landing side. The drop is most severe closest to the inside rail. Organisers have reduced the size of the fence and the drop several times in recent years in the interests of safety. It still remains a very technically challenging fence for both horse and jockey.

The Canal Turn: The challenge here is the 90 degree turn immediately following the five foot fence. Horses are unused to the abrupt change in direction on landing.

Valentine's Brook: A five foot fence with a ditch and drop on the landing side.

The Chair: At five feet two inches high, this is the highest fence on the course. It is also the narrowest and has a six foot wide ditch on the take-off side.

One theory put forward to explain the disproportionate number of falls is that the orange guide rails on the fences are incorrectly positioned and the fences themselves are too upright in design. This effectively gives the horses a misleading ground-line and causes them to misjudge the height of the fences.

So, what other factors could be problematic? The race distance of nearly four and a half miles is a very big ask of horses who, although proven stayers over three miles, are venturing into the unknown over further. Protest groups would like to see the race shortened considerably to less than four miles.

And what of the no-hopers, the two hundred and fifty to one shots? How on earth did these horses qualify for the National? A recent stipulation states that all runners must have finished at least fourth in a steeplechase of not less than three miles at some point in their career; still well short of the requirements of the great race. A minimum BHA rating of 120 is also required, although campaigners argue that the rating should be higher. Horses must be at least seven years old to qualify, presumably meaning that they will be sufficiently experienced by this age. None of these requirements guarantee that a horse will cope with the demands of the National.

So, what about the number of runners? From 1839 to 1999 the average number of runners was less than 29, although sometimes the number was greater. In 2000, a limit of 40 runners was set. Although part of the spectacle so enjoyed by the race-going public is the cavalry charge of 40 horses galloping towards the first fence; weight of numbers, speed and the consequent crowding is clearly a contributory factor to accidents.

There are calls to reduce the number of runners to below 30. This would reduce crowding and allow jockeys to find 'clear water' on the approach to the fences. There would be less likelihood of horses being impeded or unsighted as they jump.

Becher's Brook statistically causes the most casualties despite modifications and 'softening' of the fence over recent years. Protesters would like to see it removed altogether together with the drop element on all fences which is takes horses by surprise and appears to be the cause of many falls. Indeed, pressure groups are campaigning for ALL the 'feature' fences to be removed or drastically modified in the interests of safety. Their argument being that these fences are so unusual that horses are taken by surprise and effectively trapped into making mistakes.

A major cause of accidents is loose horses swept along with the field. Many either stop right in front of the fences causing a pile-up behind them, or run down the fence right in front of horses approaching. It has been suggested that out-riders could be used to try to catch up loose horses which have become separated from the main field, although the practicalities of this are open to debate.

Clearly, if the field of runners was drastically reduced, the race shortened, the fences reduced in size, difficulty and number; just an ordinary steeplechase would remain. The spectacle, the magic and the elements that make the Grand National so unique would be lost - along with the considerable revenue it generates.

So, whether you make your annual trip to the bookies to put 50p each way on the horse you drew in the office sweepstake or turn the television off in disgust at the 'carnage', the greatest steeplechase in the world is here to stay; at least for this year.