Oliver Townend enjoys his victory on Flint Curtis.
Oliver Townend, 26, took home the top prize of £100,000 for his win, riding Flint Curtis to a speedy time of 4mins 25 seconds. Lucy Wiegersma and Shaabrak were 42 seconds behind in second to claim £50,000, and William Fox-Pitt won £20,000 for third place on Ballincoola. The event, condensed into five hours, had a total prize pool of £250,000.
The event was marred by the fatal injury of Mary King's Call Again Cavalier. The horse is understood to have broken his femur. The 16-year-old gelding by Cavalier Royale was in the bronze-medal winning British team at the Olympics earlier this year.
According to British Eventing records Mary King took over the ride on Call Again Cavalier in 2005 after his previous rider, Caroline Pratt, was killed in a cross-country fall at the 2004 Burghley Horse Trials.
More than half of the field of 19 were eliminated on the showjumping and cross-country courses, designed by Pierre Michelet. The scalps included Olympic silver medalist Tina Cook and Miner's Frolic, and New Zealand's Mark Todd, whose mount Gandalf put a hole in a cross-country fence that could not be rebuilt. Todd said the "big, testing" course was too difficult for most of the horses on their first outing at such an event, including Gandalf on whom Todd finished 17th at the Olympics.
He agreed that the competition was more suited to experienced horses but said "everyone's really positive about the whole concept".
Townend was surprised at his fast time. "This has been an amazing day. I knew I could go fast, but I didn't think I could go that fast.
"The preparations for this event have been intense, but it has certainly upped my game. And, it has been great for the sport. If we can increase people's interest and enjoyment of eventing then it really is going to be a huge boost for us and our sport."
Second-placed Wiegersma said Shaabrak was "spot on" throughout. "The dressage to music was really enjoyable and the training has taken us to another level. I am sure that this is going to help me knock at least five marks off my dressage. The jumping round was really tough, but Shaabrak was spot on. He was not spooked at any stage. We took our time and it really paid off."
Fox-Pitt, in third place, said he did not deserve to win. "Oli was in a class of his own. This whole event - the exciting build up, intense training and the day itself has been like nothing I have ever experienced. It has been a great competition and one that I hope will go from strength to strength."
New Zealand's Mark Todd: competition suited to experienced horses
. © Jan Milne
"The organisers are definitely barking up the right tree," she said.
"The idea of being in the stadium and being techno-charged makes it pretty fast and furious in the arena. You need an older horse that's seen a bit more and can cope with the atmosphere - the younger horses didn't cope as well."
Lenamore, on whom Powell finished 14th at the Beijing Olympics, got a fright when the music "blasted" right next to him at the beginning of the four-minute freestyle dressage phase. They also had a run-out in the cross country.
New Zealand rider Andrew Nicholson, had three run-outs in the same phase on Avebury, and was eliminated.
The England-based rider said the new competition was "a great idea and has a lot of potential", but it needed "a few things altered to do the proper job".
He said the surface - grass planted over a thin layer of top soil on moveable pallets - was slippery and made the horses nervous; and the quick "pit-stop" tack change between the showjumping and cross country phases was too "gimmicky".
The opening dressage to music phase was won by Germany's Bettina Hoy and Ringwood Cockatoo. It was judged by Andrew Lloyd-Webber and Strictly Come Dancing judge Arlene Phillips.
Jodie Kidd won the celebrity showdown with Tara Palmer-Tomkinson.
A crowd of nearly 13,000 was at the Millennium Stadium.
"It has been an extremely exciting day with the world's top riders and horses taking part," said event organiser Stuart Buntine. "I walked around the stadium and have spoken to many people who came along. Everyone I saw loved the concept and was having a great time. We are committed to taking this event forwards."
Millennium Stadium general manager Gerry Toms said: "It was always going to be a big challenge but the 12 hour turnaround after yesterday's Wales v Australia rugby match once again showcased the versatility of the Millennium Stadium in hosting two world-class events in two days."
Organisers are looking to press ahead with plans to develop the competition into a worldwide series.