Townend, 26, completed a British clean sweep as Lucy Wiegersma claimed the £50,000 second prize, with Olympian William Fox-Pitt third.

But demanding showjumping and cross-country courses took their toll, as more than half the 19-strong field were eliminated.

And Fox-Pitt's 2008 Great Britain Olympic team-mate Mary King suffered a crashing fall on her experienced campaigner Call Again Cavalier.

King was not hurt, but the horse was taken away from the arena for further inspection, accompanied by Express Eventing vet John Killingbeck.

Townend, meanwhile, obliterated the field with a breathtaking performance after finishing fourth in the dressage section behind Germany's Bettina Hoy, King and China's Alex Hua Tian.

He finished a remarkable 42 seconds clear of Wiegersma – and celebrated in style in front of a 12,700 crowd.

"My horse was fantastic," said Townend.

"He helped me out a lot on the cross-country phase. I've never felt I had gone that fast before."

Fox-Pitt hailed Townend's performance, adding: "Ollie was unbelievable – he was in a class of his own."

The event boasted a total prize fund of £250,000, and was billed as equestrian's version of Twenty20 cricket, given its traditional three-day event format was condensed into just five hours.

Organisers and Millennium Stadium staff worked around the clock to transform Cardiff's sporting citadel that had staged the Wales versus Australia rugby union Test match less than 24 hours earlier.

British Olympian Tina Cook, an individual and team bronze medallist in Hong Kong less than four months ago, found it tough going on board Miners Frolic and was among those eliminated. "He was completely fazed by it," said Cook.