Keri-anne Payne emerged battered from the Serpentine as she finished fourth in the 10-kilometre open water swim.
Payne could not add to her world and Olympic medals as she was out-muscled, despite looking like she might reel in third-place finisher Martina Grimaldi at the death.
The 24-year-old fell just short as Hungary's Eva Risztov held off the fast-finishing American Haley Anderson for victory in one hour 57 minutes 38.2 seconds, four seconds ahead of Payne who was 0.4secs short of Grimaldi in third.
The Stockport ITC swimmer fought until the bitter end but she fell short, her energy sapped by a stop at the feeding station on the third lap and the subsequent battle to get back among the contenders.
The Johannesburg-born swimmer is as composed out of the water as she is committed in it but her mask fell when she spotted former training partner and Athens bronze medallist Steve Parry.
She sobbed before composing herself again, saying: "I thought I was all right to be honest when I was walking around until I saw Steve. He has been such a huge part of my life, training with him at Stockport, he used to take me there every morning and things like that.
"You're fine and then you see someone that really does mean something to you and it brings it all back."
Struggling to hold back the tears, Payne admitted the race had been far tougher than she had envisaged with both Risztov and Grimaldi blocking any attempted move by the Briton. She said: "It seemed to be a pretty tough, violent race from the start. I'm not really a fighter - I'm more of a lover I guess.
"I struggled in the pack with all the fighting that happened, there was quite a lot of yellow cards handed out and I got hit quite a few times in the face. I tried to deal with it as best I could but it just took a lot more energy out of me than I was expecting it to."