Funnell holds a five-point advantage over Ian Stark, who was first into the arena on the New Zealand-bred Jaybee. Heidi Antikatzides, the first Greek competitor here, rode Michaelmas to share third place with Kerry Millikin, of the United States, on Out and About.
The new method of marking, introduced in order to simplify the scoring, has so far had the effect of confusing everyone. It means higher penalties - and therefore greater differentials - in the dressage, but it will also makes the cross-country more influential as long as few horses finish within the optimum time of 12 minutes.
Hugh Thomas, the director and course designer here, was responsible for drawing up the new international rules. He believes that the present formula corresponds more closely to the ratio that was originally intended: three for the dressage, 12 for the cross-country and one for the show jumping.
Cross-country time penalties will now be incurred at one per second over the time, instead of the previous 0.4 per second. With this in mind, Andrew Nicholson, of New Zealand, - now eighth on Merillion - gave a stinging criticism of tomorrow's course.
"I think Hugh Thomas ought to give up course designing," he said. "He's gone from too many straight lines to all twists and turns; he obviously intends to make his new scoring system work no matter what."
"Not so," said Thomas. "It's true that I've tried to ensure that fewer horses finish inside the time, but that has nothing to do with the scoring system. How else do you test them when they keep getting better and better?"
The riders are naturally well aware that the time will be difficult to achieve. "Hugh has roped the course very cleverly to slow us down, we'll have to ride with our heads," Funnell said. Stark reckoned that the twisty course, with some big fences coming off turns, would require "a cross between a gymkhana pony and a show jumper."
There was an unhappy start for two of the favourites - Blyth Tait, the New Zealand world and Olympic champion, and Germany's Bettina Overesch, who holds the European title, are now back in equal 20th.
Tait had a difficult ride on Ready Teddy, who had been unsettled by the clapping that accompanied his arrival in the arena ("he was going beautifully outside but you don't get judged there").
Overesch's mount, who had the best dressage score at last year's World Games, succumbed to his old head-shaking problems and was far from his brilliant best.
Polly Phillipps, now seventh and third best of the British on Coral Cove, felt that her horse was capable of a much better test. "He felt like a time bomb, I had to be very polite to him and keep praying that he wouldn't explode."
Phillipps will receive judgement next week on the eight- hour hearing with the International Equestrian Federation's Judicial Committee which followed Coral Cove's positive test to Salicylic Acid at a level above the permitted threshold at last year's World Games.
"The horse has been so difficult over the last couple of days that I've had plenty to worry about without thinking of that," Phillipps said.
MITSUBISHI MOTORS BADMINTON HORSE TRIALS (Glos): Results after first day of dressage: 1 Supreme Rock (P Funnell, GB), 64 penalties; 2 Jaybee (I Stark, GB), 69; 3 Michaelmas (H Antikatzides, Gre) and Out and About (K Millikin, US), 70; 5 Rimini Park Fabian (E Stibbe, Aho), 77; 6 Word for Word (M Todd, NZ), 79; 7 Coral Cove (P Phillipps, GB), 80; 8 Merillion (A Nicholson, NZ), 82; 9 Eurodollar (C Lomax, GB), 84; 10 Westlord (P Clark, GB), 87.