Britain's Leslie Law, elevated to individual gold medallist in the three-day event, says he will apologise to the German, Bettina Hoy, whom he displaced when she lost both individual and team titles on appeal.
"It feels pretty good actually, very exciting," Law said. "But I know Bettina quite well and I'm sure she's going to be extremely disappointed."
Law, 39, sees Hoy frequently on the eventing circuit and he says their next meeting will be difficult. "I will say I'm sorry, it's as much as I can do."
Hoy had initially received 12 time penalties for crossing the starting line twice during the showjumping phase but that decision was overturned and Hoy, and Germany, went on to receive the individual and team titles.
However, on Saturday Law was elevated from silver to gold medallist when the Court of Arbitration for Sport upheld an appeal by France, Britain and the United States.
His team-mate Pippa Funnell now collects an individual bronze and the British team, which also included William Fox-Pitt, Mary King and Jeanette Brakewell, move up to silver.
Law, who rode Shear L'Eau to the gold, revealed he had once made the same mistake as Hoy. "It was about eight years ago in France and I collected penalties for it. I know exactly what it feels like but just not at such a high level."
The British showjumper, Nick Skelton, who once feared he would not ride again, hopes he can deliver a second equestrian gold.
He suffered a serious neck injury days before Sydney 2000 and spent months in hospital. However, a superb clear round on Arko III, with only one time fault, left him well placed after the first phase of showjumping qualifying. He was 11th overall but within touching distance of the leaders. Robert Smith and Mr Springfield incurred four faults, leaving them 19th.