New Zealand's master horseman Mark Todd is in line for his fifth Olympic medal, finishing the cross-country phase of the three day event in third place.
In a very tight competition at Greenwich Park on Monday, Todd rode a clear round on Campino but picked up a minor time penalty which cost him the lead.
He is just 0.2 penalties, or less than a showjumping rail, behind joint leaders Ingrid Klimke of Germany and Sweden's Sara Algottson Ostholt.
Andrew Nicholson is in 9th place and Jock Paget 14th in the individual competition.
Todd, 56, who is competing in his seventh Olympic Games, has previously won two gold and two bronze medals at Olympics.
Former Olympic equestrian medal winner Vaughn Jefferis says Todd showed immense talent in a masterful ride on such a young horse.
"That was a young horse and it was a long course and the horse showed his greenness out there but Mark absolutely showed his experience."
The New Zealand team is also in with the chance of a medal, remaining 4th place overall, less than one showjumping rail out of the silver position.