The British athlete said it became clear to her from about two miles into Sunday morning’s race that her hip – which had begun feeling tight three weeks previously – was going to be “really, pretty painful”.
She ended up crossing the line with a stress fracture of her femur.
“It was really tough,” Harvey told the BBC.
“The hills didn’t help at all, the downhills were just agony and it just got worse and worse. At the halfway mark I knew it was going to be incredibly painful.”
Despite treatment for her hip before the Olympics, the injury did not appear to be getting any better.
Doctors and physios told Harvey that running the marathon would make it worse – but there was a chance that she could get through it and do her training justice.
With no Team GB reserve available to fill her space, Harvey decided to attempt the event and felt positive on the start line.
Six miles in, though, she was falling behind the pack and soon running on her own.
But Harvey, who was selected after running 2:23:21 in Chicago last year – just 26 seconds shy of Hassan’s finishing time in Paris – fought through the pain to complete the event ahead of two other runners. Eleven more did not finish.
“The Olympic energy was kind of what kept me going to that finish line,” she said.
“Any other race I would have stopped, because I wasn’t able to run like I normally can… and the pain was really bad, but I just had to get to that finish line, I had to do the Olympic marathon.”
Harvey says she now cannot put any weight through her leg at all so is not sure how she finished. But the athlete highlighted gaining “grit and resilience” from her training, having friends and family in France and the “incredible crowds” as helping her.
She said the thought of her fiance, Charlie Thuillier, also kept her going.
“Every mile, I just thought ‘right, just run to Charlie, run to when I can see him next’.”