Two horses suffered fatal falls in this year's Grand National at Aintree, prompting criticism that the course is too hard. So how dangerous is it?
The Grand National is billed as the "ultimate test of horse and jockey" by its organisers, as well as the world's most famous steeplechase.
This year two horses died in the race. Ornais suffered a fatal fall at the fourth fence and Dooneys Gate at the sixth.
The deaths have prompted some to call for an end to the historic race, with animal rights groups saying it is cruel. So how dangerous is it?
The Grand National carries a higher risk than a lot of other horse races for several reasons. It is a steeplechase, which is more dangerous than flat and hurdle racing. On top of this, it is also longer than the average race with more fences to jump, 30 in total.
The risk of horse fatalities in a steeplechase is around six per 1,000 starts, says Dr Mark Kennedy, senior lecturer in animal welfare at Anglia Ruskin University. This is compared to approximately one per 1,000 horse starts for flat racing and four per 1,000 horse starts for hurdling.
"On average in the larger jump meetings, such as the three-day Grand National event, we can expect around three horse fatalities," he says.
"My point is these are not freak accidents, they are predictable. If the risk to the car driver was the same as the Grand National - six deaths in 1,000 - then you would be lucky to still be alive after six months.
"I am not an abolitionist who thinks the race should be banned, but risk in the Grand National is high and you will never be able to get it down to zero."
The British Horseracing Authority (BHA) says the university's estimates are "broadly correct". But according to its own figures for the actual all-important Grand National race, from 2000 to 2010 there were six horse fatalities. This covers 11 runnings of the race, with 439 horses starting. This puts fatalities higher than Dr Kennedy's six per 1,000 starts statistic.
This could be down to the length of the course, says the BHA. The longer it is, the harder it can be because horses and riders get tired. The Grand National is longer than most other steeplechases, which are usually between 2 and 3.25 miles. It is two full circuits of the Aintree course, making it 4 miles and 880 yards (7,242m) in total, according to the racecourse.
The higher number of fences is also a factor as jumping obstacles increases risk, says the BHA. The only race believed to have more fences than the Grand National is the Velka Pardubicka in the Czech Republic, which has 31. Some of the fences in the race are also very challenging, with organisers themselves saying the riders face "the most testing fences in the world of jump racing".
The ground on the day can also be an issue, with certain conditions allowing horses to go faster and be at more risk. Extensive watering takes place at Aintree in the build-up and during the race meeting to make sure the ground is not too hard.
Dr Kennedy also argues pressure could be a factor. "The Grand National can be a career-changing moment if you win it, the ultimate achievement. This can put pressure on jockeys and they might be tempted to push things in a way they wouldn't in other races."
Each year Aintree reviews safety, working with animal welfare organisations. In 2008 consultations with the RSPCA led to the fences being trimmed in width to allow horses to go round them. This came into use for the first time this year, after the two horses went down in the first circuit of the course. Drops on the landing side of fences have also been reduced.
"This is a well-organised and professional meeting, we do not take unnecessary risks," says a spokeswoman for Aintree. "We plan for 12 months to make sure the race meeting goes as safely as possible. As with any sporting event, we cannot make it risk free, but we endeavour to minimise that which we can control. We believe the Grand National is a tough but fair test for horses."
But some argue some new safety measures have actually made the race more dangerous.
"It's speed that does the damage, the faster they go, the heavier they fall and the more likely they are to fall," says Ginger McCain, the four-time Grand National-winning trainer whose son trained Saturday's winner Ballabriggs.
"You don't make things better by making it easier."
Horse owners and trainers say there are risks in racing, just like anything in life.
"Although this is a great sport, accidents can happen," says Paul Nicholls, who trained Ornais, one of the horses that died on Saturday.
"Like one paper said this morning, it doesn't matter how safe you make the M1, the M4, the M5 or whatever, you're always going to have accidents."