Stylish American rider Clark Montgomery thrilled the capacity crowd at the Mitsubishi Motors Badminton Horse Trials (GBR), fourth leg of the FEI Classics™ 2013/2014, when he deservedly took the lead. His dressage test was a model of balance, consistency and harmony despite the wind that has battered the Gloucestershire site all day.

Montgomery, 32, was third last to go on William and Holly Becker’s 11-year-old Loughan Glen and scored the excellent mark of 33.5 penalties. This gives him a 2.5-penalty advantage over Australia’s Paul Tapner and Kilronan, who had until then maintained the lead since yesterday.

Francis Whittington (GBR), the highest placed of the home side, is now in third place on Easy Target, just 0.2 penalties behind Tapner.

Montgomery is based in England, just down the road from Badminton with CCI4* judge Christian Landolt (SUI). “The horse has put in some good marks before and I knew he was capable of this standard if all went well,” said Montgomery of the Limerick-sired bay gelding on which he finished third at Blenheim CCI3* (GBR) last year.

“He should like the Cross Country course,” added Montgomery. “He likes to be ridden forward and hopefully he will cope with the step up, although I don’t know yet whether the [optimum] time will be an issue for him.”

The three top-placed horses are all Irish-bred, which may be an advantage if the rain which is forecast to fall tonight materialises. “The ground will definitely suit my horse and I’ll be quite happy if it keeps on raining!” said Tapner.

Lucinda Fredericks (AUS), who scored the only other sub-40 mark, is now fourth on Flying Finish, just ahead of Sir Mark Todd (NZL), the oldest rider in the field (at 58) and the only one to have two horses in the top 10. The four-time Badminton winner is equal fifth on NZB Campino and equal ninth on the 10-year-old Leonidas ll.

Six nations are represented in the top 10. Olympic silver medallist Sara Algotsson-Ostholt (SWE), who is paying her first visit to Badminton, is in equal fifth place with Todd on 40.5 with Reality 39 (formerly called Mrs Medicott), on which she won a team silver medal at last year’s FEI European Eventing Championships.

William Fox-Pitt (GBR) was a happier man after scoring 41.0 on Parklane Hawk. His first ride, Cool Mountain, disappointed and is in equal 57th place, which leaves him in equal seventh place with Andrew Nicholson (NZL) on Nereo.

Danish rider Peter Flarup made a great start to his first Badminton and is in equal ninth with a score of 41.8 on the Danish warmblood mare Callista E, on which he was 12th at Boekelo CCI3* (NED) last year. Flarup, who has been riding at championship level since 1997, had his best CCI4* result at Pau in 2010 on Silver Ray.

Nearly half the field of 83 scored under 40 penalties in the Dressage, thus ensuring a thrilling day tomorrow.

The big news for riders is that the middle element of fence 18abc, a trio of logs on an S-bend which was proving a hot topic, has been removed. This would have involved a sharp right-hand turn at the foot of a mound, and the organisers decided that the heavy rain that is forecast might make the turn slippery.

Mary King (GBR), who first competed at Badminton in 1985, said: “I thought it was a great fence and well-designed, but I can see why the decision has been made.”

King, who first won Badminton in the very wet year of 1992, produced her best Badminton test on the ebullient 17-year-old Imperial Cavalier, on which she was third in 2011 and fourth in 2010. She earned the loudest cheers of the day and is now in 12th place on 42.8.

Her performance was only marred by an error of course in the extended canter. “I’m over the moon with him,” she declared. “It’s the best test he’s ever done here. He was so rideable. I was enjoying it so much that I then managed to go wrong.”

Kristina Cook (GBR), who has been competing at Badminton for more than 20 years and is in 23rd place with a mark of 45.8 on her home-bred De Novo News, pronounced the Cross Country course to be “super”.

She said: “It’s bigger and wider, very much a Badminton course to give us sleepless nights. They’ve done everything they can with the ground and there’s a great grass cover. You’ve got to be bold and brave and keep pushing, and the riders that can achieve that will do the best.”

Results after Dressage

1 Clark Montgomery/Loughan Glen (USA) 33.5 penalties
2 Paul Tapner/Kilronan (AUS) 36.0
3 Francis Whittington/Easy Target (GBR) 36.2
4 Lucinda Fredericks/Flying Finish (AUS) 39.0
5 = Mark Todd/NZB Campino (NZL) 40.5
5= Sara Algotsson-Ostholt/Reality 39 (SWE) 40.5
7 = William Fox-Pitt/Parklane Hawk (GBR) 41.0
7 = Andrew Nicholson/Nereo (NZL) 41.0
9 = Peter Flarup/Callista E (DEN) 41.8
9 = Mark Todd/Leonidas ll (NZL) 41.8

Full results here.