Ruth Edge, a reserve rider for Great Britain at the Beijing Olympic Games last month, briefly illuminated a dank, rainswept day at the Land Rover Burghley Horse Trials with a sparkling dressage test on Mr Dumbledore, William Fox-Pitt's former horse, to take a commanding 5.4-point lead.

Lucy Wiegersma on Shabraak, her Badminton runner-up, and Fox-Pitt on Tamarillo, his former Britain team horse, are second and third as the competition moves on to the demanding, stamina-sapping cross-country phase. Fox-Pitt, who is bidding for a fifth win, said that the event is “the wettest Burghley I can remember”.

Edge, who had the advantage of going first on the second day of the dressage yesterday before the relentless rain had turned the arena squelchy, was “thrilled” with her performance on the 12-year-old gelding. “He's a show-off and seems to grow when he goes into the arena,” she said.

Zara Phillips, employing new tactics on Ardfield Magic Star - her second ride who finds dressage difficult - did not get on the horse until the last minute to stop him becoming too excited. Although she is 22nd, Phillips was not discouraged. “It worked,” she said. “It was one of his better tests.” Both her horses - she is equal 42nd on Glenbuck - are noted crosscountry performers, which should serve her well today on the 31-fence course designed by her father, Captain Mark Phillips.

Fox-Pitt, whose test on Tamarillo in the worst of the rain earned him 39.8points, his best result at this level, does not underestimate the task ahead. “If it's soft, there are bound to be lots of time faults,” he said.

Captain Phillips announced last-minute changes to the course last night to reduce the jumping efforts. He has removed fence ten and the last element of The Leaf Pit (fence 4c) and amended two other fences. “We'll have a team on the course at 7am to see how much gravel to put down to stop it becoming slippery,” he said.

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