Twenty/20 (With horses)

Eventing is the latest sport to take a crammer course with unprecedented rewards for the winner. Genevieve Murphy previews tomorrow's launch in Cardiff which hopes to attract a whole new audience

Cricket has done it, so why not horses? That's the idea when eventing is given a Twenty20 makeover in Cardiff tomorrow, shoe-horning four days into a frantic four hours with the biggest cheque in the sport – £100,000 – going to the winner.

The prize, which is £40,000 more than a rider could have won at Badminton – hitherto the richest reward at a single fixture – is part of a revolutionary, but strictly non-gimmicky, concept that has attracted 20 leading riders from around the world, including Britain's Mary King.

Throw in dressage judge Arlene Phillips, fresh from galloping all over John Sergeant's hoofing on Strictly Come Dancing, and the Millennium Stadium is in for a special day. Another judge at the event, which is costing more than a £1m to stage, is Andrew Lloyd Webber, whose wife, Madeleine, used to event.

King, who will be riding her Olympic team bronze medal partner, Call Again Cavalier, is preparing for the Express Eventing International Cup with typical event rider's enthusiasm, enlisting the aid of the top dressage trainer Ferdi Eilberg for her first freestyle to music. She is enjoying learning new movements, such as pirouettes, as well as the challenge to match music and movement.

Riders will start with a freestyle dressage test to music, now a regular part of "pure" dressage, but new to most event competitors. Dressage scores will have been converted into seconds (one mark equalling two seconds) before competitors return to the arena for the final show jumping and cross-country.

These two phases, plus the intervening pit stop during which riders change into cross-country gear, will be timed as one entity and run in the reverse order of merit. As in traditional eventing, penalties will be incurred for each lowered show jump and for refusals across country.

All competitors have been supplied with a specially designed show jumping jacket that is fastened with poppers allowing it to be whipped off smartly during the all-important pit stop change, which should take an average of 45 seconds.

On previous form it must be assumed that Germany's Bettina Hoy will be last to go in the show jumping and cross-country, since her grey mount, Ringwood Cockatoo, is in a class of his own in dressage.

But the 17-year-old gelding, who won the four-star contest at Pau in France last month, could still need to get his skates on if he is to remain in front.

Hoy's elite opponents include the winning riders from other four-star competitions this year – Philip Dutton, of the United States, who triumphed in Kentucky, the French European champion, Nicolas Touzaint, who won at Badminton and William Fox-Pitt, who carried off the top prize at both Luhmuhlen and Burghley. Also competing are Australia's Clayton Fredericks, who won this year's World Cup final in Deauville, and the legendary New Zealander Mark Todd, who was individual Olympic champion in 1984 and 1988.

The event is the brainchild of Stuart Buntine, who had been playing with the idea for more than a decade. The Australian (who is a former international competitor and organiser of the hugely successful event at Belton Park in Lincolnshire) reckons that "everyone in the sport is a complete adrenalin junkie".

Buntine hopes that the experience will win new spectators for traditional eventing rather than steal them away. "I want to promote the sport by taking it to the people," he said.

It was while the concept was ending its long period of gestation that Buntine delivered a daring challenge – "I was foolish enough to say: 'If you find me a stadium, I'll create a competition'." He had looked at various venues, both indoors and out, before he saw the Millennium Stadium and knew that his idea was off the ground. Needless to say there are still problems to overcome. First comes the seemingly nightmarish logistical challenge, which requires a herd of course builders to move into the stadium tonight after the Wales against Australia rugby union Test in order to create the cross-country course, which includes two water complexes, by 7am tomorrow. Fortunately, holes in the turf – whether made by horses' hooves or the construction of water complexes – will not matter as the whole lot is scheduled to be dug up and replaced on Monday.

Only the top two of the stadium's three tiers will be used, giving spectators a unique bird's eye view of the action. But it seems unlikely that the ticket sales will go anywhere near to filling the 42,000 seats available, so questions remain.

Can there be enough of an audience to provide the electric atmosphere required to drive Buntine's imaginative concept forward to its worldwide goal? Will it make dynamic television for Sky Sport, who will be transmitting the contest the following Friday?

The riders, as much as Buntine, will be hoping the event clears the first fence. "I would love the first one to be a success," King said. "It could give us something really exciting to do through the winter months."

Millennium stars: Three to watch

Mary King, who teamed up with Call Again Cavalier in 2005, regards this talented all-rounder as the best horse she has ridden. King was an eager teenager when she went to three-times Badminton winner Sheila Willcox as a working pupil and she remains as keen as ever as a 47-year-old. King's medal collection includes five team golds – one from the World Equestrian Games and four from European Championships. She has also ridden in five Olympics.

Nicolas Touzaint, who won his two European titles in 2003 and 2007, became the first Frenchman to triumph at Badminton when he won the annual classic in Gloucestershire this year. The stylish 28-year-old, who is a gifted all-round horseman, returns to Britain with his victorious Badminton mount, Hildago de l'Ile. Touzaint was runner-up on home soil in the four star competition at Les Etoiles de Pau last month when he rode Tatchou to finish just 0.5 of a penalty behind Bettina Hoy.

William Fox-Pitt would be putting the final touch to his remarkable year if he were to scoop the prize tomorrow. The 39-year-old, who made his career in eventing in 1993 after graduating in French at the University of London, will be riding Ballincoola – the winner in 2005 at Burghley, where Fox-Pitt was runner-up in September when he won on his other mount, Tamarillo. Thanks to his Burghley and Luhmühlen victories, he has already claimed top prize in the HSBC FEI Classics.

Four-hour eventing Timetable

*11.00am: Opening ceremony and dressage masterclass with Carl Hester

*11.20am: Freestyle dressage to music

*1.00pm: Lunch interval with arena entertainment (includes celebrity jump-off with Jodie Kidd and Tara Palmer-Tomkinson)

*2.00pm: Riders' course walk for show jumping and cross-country

*2.15pm: Show jumping and cross-country phase

n3.15pm: Interval

*3.30pm: Show jumping and cross-country continues

n4.30pm: Prize-giving