The British athlete said she realised about three kilometres into the race on Sunday morning that her hip – which had felt tight three weeks earlier – was going to be “really, quite painful”.
She crossed the finish line with a stress fracture in her femur.
“It was really tough,” Harvey told the BBC.
“The hills didn’t help at all, the descents were just torture and it just kept getting worse. Halfway through I knew it was going to be incredibly painful.”
Despite treatment for her hip before the Olympics, the injury did not seem to improve.
Doctors and physical therapists told Harvey that running the marathon would worsen her condition – but there was a chance she could pull through and do justice to her training.
With no Team GB substitute available to take her place, Harvey decided to take part in the competition and started off feeling confident.
After ten kilometers, however, she fell behind the field and soon had to run alone.
But Harvey, who was selected after running a time of 2:23:21 in Chicago last year – just 26 seconds slower than Hassan’s time in Paris – fought through the pain to finish ahead of two other runners. Eleven other runners did not finish.
“It was the Olympic energy that kept me going until the finish line,” she said.
“Any other race I would have stopped because I couldn’t run like I normally do… and the pain was really bad, but I just had to get to the finish line, I had to run the Olympic marathon.”
Harvey says she can’t put any weight on her leg now and isn’t sure how she managed it. But the athlete stressed that the training gave her “courage and perseverance” and that friends and family in France and the “incredible crowds” helped her.
She said the thought of her fiancé, Charlie Thuillier, also helped her to carry on.
“Every mile I just thought, ‘Okay, just run to Charlie, run until the next time I can see him.'”