British-based American rider Tiana Coudray riding Cancaras Girl scored a personal best dressage score on the first day of MARS Badminton Horse Trials and is now in the lead at this early stage of the competition.The ground jury president Christina Klingspor (SWE), Amanda Miller (USA) and Angela Tucker (GBR) awarded only three sub-30 marks.Tiana is on 28.1 penalties, with Britains Will Rawlin (Ballycoog Breaker Boy) on 29.3 and the mornings leader, Bubby Upton riding Cola, scoring 29.8.Two Irish riders, Georgie Goss (Feloupe) and the 2024 runner-up Lucy Latta (RCA Patron Saint) are fourth and fifth and Britains Sarah Bullimore is currently in sixth place on the home-bred Corimiro.This is Tianas third Badminton with the Holsteiner mare Cancaras Girl who came from a show jumping yard 10 years ago and was originally for sale as a junior horse. She was a horse I saw on Facebook she was small, pretty and polite but never flashy and in the end I didnt sell her, Tiana explained.It is a privilege to be here a third time and I will be as competitive as I can be. Everything is the icing on the cake with her.Wiltshire-based Tiana, 37, is from California, where she competed in Irish dancing at world championship level. She began eventing through a school programme and came to England in 2011, representing the US at the 2012 Olympic Games.Will Rawlin, 32, is also competing at a third Badminton with his ride, the Irish Sport Horse Ballycoog Breaker Boy. Like Tiana, he lives in Wiltshire and is trained in dressage by Tracie Robinson.Ballycoog Breaker Boy felt fantastic coming into Badminton, said Will. He has had a good spring lead-up and I am very chuffed. We had a few mistakes, but there is plenty more to come.Newmarket-based Bubby Upton, who made a courageous recovery from serious spinal injury in 2023, has produced the 16-year-old Cola all the way from BE100 level through winning medals at the Young Rider Europeans to five-star level. To be here together for the fifth time is very special, she said. He is a horse that has fulfilled so many dreams.Todays riders are already looking ahead to Saturdays cross-country phase. Eric [Winter, course-designer] is an absolute genius, said Bubby. Its a helluva track, big intense and will get us thinking.Experienced five-star rider David Doel, who is lying 28th on his first ride, Ferro Point, said it was one of the fairest Badminton tracks. The combinations come up clearly to the horses and it should ride nicely. It is still jolly big, though!Dressage recomences at 10am tomorrow. World number one Harry Meade will be first into the arena with his second horse, Annaghmore Valoner.Ros Canter and Lordships Graffalo begin their title defence at 10.48am in front of HM The Queen, who is attending Badminton in her capacity as patron of the events designated charity, the Ebony Horse Club.Follow the competition on Badminton TV and Radio Badminton.