The Rio 2016 team eventing gold medallist produced an impressive test on his horse Qing du Briot.

Their score of 38.7 points marked an impressive start to the competition for the duo, who are competing at the event in Britain for the first time.

"I had hoped very much that he would express all his qualities today," Vallette said.

"He’s quite sensitive and there is plenty of atmosphere in the arena.

"Plus, it was his first proper four star so I was very happy with his performance."

Germany’s Bettina Hoy lies in second place, after achieving a score of 39.2 points on her horse Designer 10.

The leading two riders will be looking over their shoulder, with defending champion Michael Jung poised in third place after the first day.

Riding on La Biosthetitique Sam, Germany's three-time Olympic gold medallist was able to end a score of just 40 penalties.

Jung, who completed the grand slam of eventing by winning the 2016 event, will hope to close the gap to the leaders tomorrow.

The grand slam of eventing is made up of the Kentucky Three-Day Event, Badminton Horse Trials and the Burghley Horse Trials.

Jung came into the Badminton Horse Trials in confident mood after winning the Kentucky Three-Day Event last weekend for the third consecutive year.

The second day of dressage will be the focus of attention tomorrow, as the competition reaches the halfway stage.

The cross-country test is then due to take place on Saturday (May 6), before the Badminton Horse Trials conclude with the jumping test the following day.