Oiwa, who is already a three-time Olympian, jumped from third to first on Bramham’s final day on board Calle II as Britain’s Gemma Tattersall and Quicklook V squandered victory by putting one fence down in the last showjumping round.
A clear would have given Tattersall victory, but both the British rider and Australia’s Sammi Birch on Hunter Valley II blew their chances by putting one rail down each, meaning they would finish second and third.
Northallerton’s world No 10 Nicola Wilson put two fences down on One Two Many, dropping the London 2012 Olympian from fifth to eighth after resurrecting her prospects with Saturday’s perfect cross-country round – the only one of the day inside the time in the CCI three-star.
Grafton’s James Sommerville jumped one place above Wilson into seventh to finish as the highest-placed Yorkshire rider on the appropriately named Talent.
But Oiwa, 40, was to prove an appropriate winner three years short of the Tokyo 2020 Olympic Games.
“I am very happy with the result as I just didn’t expect to be winning here,” said Oiwa, who is spending the summer based at Pippa Funnell’s yard in Surrey.
“In probably two or three days it will hit me with what I did. It will probably make me even more happy when I get home and hear about it from friends.
“I wanted to be competitive and my goal was to finish in the top ten or top five. I didn’t expect to be winning.”
Wilson and One Two Many were sat down in 28th after Friday’s disappointing dressage test, but the only perfect clear cross-country round of the entire CCI class propelled the combination into the top five on a dramatic Saturday afternoon.
Wilson appeared to be moving fourth when news then emerged that Friday night leader Tattersall had been hit with a 50-point penalty for falling foul of the new flag rule over her cross-country test on Quicklook V.
The penalty threatened to dump Tattersall from first to 30th, but the rider was successful in her appeal, leaving her 1.7 penalty points ahead of Birch heading into the showjumping finale.
But the rarity of Quicklook V putting a rail down ended Tattersall’s hopes of a first CCI win at Bramham.
“It’s the first rail she’s ever had down at a three-day event,” revealed Tattersall. “It’s hard luck, but that’s our sport.”
Huddersfield’s world No 7 Oliver Townend saw his chances officially ended when his sole remaining entry Note Worthy eventually retired from Saturday’s cross-country test.
The Bishop Burton College CCI three-star Under-25s event was concluded yesterday morning with young Briton Will Furlong surviving a nervy show-jumping round to win the class on Collien P 2.
Furlong put two fences down and added one time penalty, but still edged out fellow Briton Gina Ruck on Rehy Too with Alicia Hawker next on Charles RR as part of a British one-two-three.
“I think I had 11 penalties in hand and I think I used nine of them so it was quite tight at the end. I’m pleased I had that buffer,” said a clearly relieved Furlong.
York’s Hector Payne finished 11th on Dynasty, while Bedale’s Caroline Clarke came 13th after enjoying a Bramham double clear on Touch Too Much, who picked up just 42.8 time penalties over their cross-country test.
Payne’s other mount, Ironstein, was eliminated over Saturday’s cross-country, which also eliminated Bedale’s Charlie Dennis on DHI Hot Chip and Womersley’s Sophie Platt on Be Be III.
The CIC three-star class was concluded on Saturday evening as British star Izzy Taylor enjoyed her first win at the venue on Trevidden.
Taylor swooped to glory despite being sat only 15th after dressage after producing a double clear over showjumping and cross-country with no time penalties in either.
“I’m delighted to have the win, absolutely chuffed,” said Taylor. “Bramham is one of favourite events, which makes it more special.”
Wilson was well placed to challenge for victory on Kings Advocate II, who was fifth after dressage, but the Northallerton rider withdrew the 10-year-old before cross-country.
Australia’s Paul Tapner finished second on Yogi Bear VIII, while New Zealand’s Tim Price came third on Cekatinka.
The USA’s Tiana Coudray was the only other CIC entry to go clear over cross-country inside the time, elevating her to fifth on Under The Clocks.
Zara Tindall had to settle for finishing 14th on Fernhill Facetime, while Harrogate rider Hazel Towers enjoyed two clear cross-country rounds on Simply Smart and Simply Clover .
This was enough to give her two finishes inside the top 30 to become top Yorkshire rider in the CIC.
Simply Smart consequently jumped from 64th to 22nd with Simply Clover moving from 68th to 27th.
Bedale’s Sara Bowe was eliminated over the cross-country test having fallen from 34th to 62nd after picking up 23 penalty points in Saturday morning’s show-jumping round. Friday night leader Tapner picked up eight penalty points in the showjumping and was then eliminated over the cross-country.